Z-3: 1941, Amazing Man Comics #24 (Centaur). Agent of a foreign dictatorship (read Nazis) stationed in the US. He is sent by the leader to steal the supposed death-ray created by Bruce King (in actuality it's his Black Zero transmitter, a dark light of intense cold). When his three men fail and are killed, Z-3 assassinates them.
Zahinda the Legless: 1947, Jungle Comics #87 (Fiction). According to Durrant: Zahinda the Legless was a big brutal man who had no legs and so rode on the back of a zebra. He tried to kill Ka'a'nga in order to usurp the rule of the jungle for himself, but only succeeded in blinding him. Then he raided the very trading post where Ka'a'nga was being treated for his injuries and abducted Ann, his mate. Despite his injuries, Ka'a'nga rose from his sickbed and tracked Ann and Zahinda down, then rescued Ann from the mine where Zahinda kept slaves working day and night to mine valuable ore. Zahinda died when his zebra was gored by the ox that had been pulling the carriage that had brought Ka'a'nga to the mine. Once Zahinda was on the ground, the ox gored him too.
Doctor Zandricks: 1943, Shadow Comics v2n11 (Street & Smith). Zandricks and his animal men were defeated by the Hooded Wasp.
Zarita: 1941, Fight Comics #12 (Fiction).
On a jungle coastline, Zarita heads up the Black Sword Cult
operating out of an estate built during Spanish dominion.
The cult members and/or victims are branded on the neck with a small black sword. The victims are killed
by her pet, a deadly swordfish. When jungle fighter Oran defeats
her men and kills her pet, she chooses suicide over capture.
Dr. Ignatio Zaroff: 1939, Amazing Mystery Funnies #8 (Centaur). A spymaster at the beginning of WWII and father of Dacia Zaroff. He ran a small efficient espionage ring that ran afoul of Barry Finn.
Honest John Zazabo: 1943, Jungle Comics #41 (Fiction). Anthony Durrant writes: Honest John Zazabo was a trader who was about to retire; a tribe nearby held a farewell ceremony for him in which John passed out gifts to the men; his real plan was to drug the punch he was giving to the male villagers and abscond with their diamonds. Camilla, the jungle queen, tried to stop him, but was caught by honest John and tied up near a huge anthill. Released by her friend Mala, Camilla rallied the women and they drove Honest John and his men into a nearby swamp, then dropped the jewels and the men into the murky water to get rid of them for
Baron Zborov: 1941, Wings Comics #11 (Fiction). While flying important military papers to Cyprus, a storm forces Suicide Smith to crash in Transylvania. When he comes to, he finds himself a prisoner of Baron Zborov's in a medieval castle. The baron's hulking assistant Otto confides to him that the baron and the beautiful Hinda are vampires. However, Hinda reveals herself as a British agent and that Zborov is high with der Fueher. Smith escapes, shooting the baron in a dogfight and takes Hinda to the French Resistance in Paris, where he promptly runs into a little trouble with the Gestapo. It should be noted that Hinda didn't dispute the claims of vampirism and Zborov lived to fight the very next issue.
Zog, Prince of Mars: 1940, Amazing Man Comics #15 (Centaur). Zog and his men are teleported to earth by some strange race of men on a mysterious island. Zog promptly kills the scientist responsible with a strange beam and starts to bring more of his race to Earth. Only, the Shark (who, with his pop, had been captured earlier by the island's strange inhabitants) managed to outfight him and wreck the teleportation machine. Their vulnerability to water was discovered when he threw water on them to revive them.
Zolok: 1935, The Lost City (Sherman S. Krellberg)/ Comic: 1942, Great Comics #3 (Great Publications). Zolok is the last of the Lemurians in a lost city. Zolok desires to take over the world. He holds brilliant scientist Dr. Manyus and his beautiful daughter Natcha hostage and forces the scientist to create giants from the natives, including the "six-armed crusher" and other weapons. His right-hand man is Appolyn. However, his plans are discovered by a group of men headed by Bruce Gordon. NOTE: Originally an independently produced serial, it was partially adapted into the comics, part 1 in Great Comics #3 and part 2 in Choice Comics #3. Don't know if there was ever a part 3. Not sure the accuracy of the adaption where some of the story info comes from, as a giant six-armed man would be really hard to pull off but looks pretty good in the comic.
The Zombie: 1947, Thrilling Comics #62 (Better). Jim Allen and Kenneth Barr witness a voodoo ceremony in Haiti and bring back Ogoun, the zombie. However, a curse is on them for kidnapping the undead corpse, that when it woke it would get revenge. Sure enough, when the ceremony is re-enacted and the zombie wakens, it kills Barr. Then others who witnessed the dance, like "Clarion" publisher Frank Havens are sent threatening notes. This gets the Phantom Detective involved. He discovers it's all a plot by Jim Allen, that the ceremony was fake, knowing that Barr would fall for it. The Zombie is nothing more than a murderous half-wit from Haiti made up that Allen thought he could use for blackmail. Only the Zombie was harder to control than he thought and tended to kill instead of bringing money back.
Zombie Master: 1945, Catman #29 (Holyoke). The Zombie Master looks more like a gypsy fortune teller, wearing a turban, dark suit, monocle and sporting a pointed beard and curled mustache. However, he's in the service of Khara-El whose spirit demanded a human sacrifice. He came to the States and performed a dance of Damballa, knowing his intended victim would be drawn to him. He was soon rewarded by nightclub singer Ellen Cole presenting herself. However, when his powerful dark servent Kuala kidnapped her, the Deacon and Mickey intervened. Kuala easily manhandled them but was shot by a cop and died before the Zombie Master. He rose Kuala as a zombie just in time to fight the Deacon and Mickey once more who had followed the blood trail. Again, the Deacon is no match for Kuala's inhuman strength but when Mickey punches the Zombie Master, the man dies and his zombie with him. Was the Zombie Master truly that frail or just an unlucky punch or was he killed by his god for failing in the sacrifice?
Zombies: 1940, Speed Comics #11 (Harvey). Their origins are unknown, but when Comrade Ratski meets up with Baron Von Kampf, the so-called zombies are under the command of Von Kampf. They are not the mindless undead, but something else entirely. These zombies look a bit like the Heap in that they are large, furry or grassy as they are green, but have large ears and one eye. And, they speak, though their sentences are backwards. They seem to have normal intelligence as they can use guns, gas masks, parachutes, and radios and able to make their own decisions. When one group is unable to outfight Shock Gibson, they surrender to him. After the destruction of the Florida headquarters, what Shock Gibson chooses to do with them is unrevealed.
Zora: 1941, Super-Mystery Comics v2 #3 (Ace). Considering herself a superior woman, Zora seeks out the Clown (a superior man) as a criminal partner. Her father has a factory, and she is a highly trained chemist seeking revenge on the world due to how it's treated her and her inventions. She has invented a pistol that shoots a blinding incapacitating chemical. She proves to be good at disguise and acting, passing herself as Davy's sister Beatrice. Ultimately, Magno and Davy put an end to their plans and he is able to tell her apart from Beatrice by her older hands. In escaping, the Clown knocks her out and throws her and a dummy disguised as him into a river while he hides. Magno and Davy arrive in time to see the two bodies disappear and assume the villains committed suicide.
Dr. Zorn: 1940, Thrilling Comics #5 (Better). The Three Comrades (Lucky, Cal, and Books) are on vacation in Puerto Rico visiting Tom Carroll, an old friend of Cal's and Tom's sister Caroline (Caroline Carroll?). However, there's a mysterious man on the island, the bespectacled and bewhiskered Dr. Zorn. Turns out Tom owes him a lot of money and he plans on taking over the coffee plantation where he also has his secret lab with a voice activated robot. Then from there, he's set to take over the world. However the three young men manage to destroy the robot and Dr. Zorn is electrocuted when he tries to self destruct his lab.
Zuko, the Bird King: 1941, Jungle Comics v2 #22 (Fiction). In the tall trees of the swamp is the lair and domain of the native Zuko. Under Zuko's command are large vulture-like birds and he makes use of wings attached to his arms to glide through the air. He teams up with Sawabi, the witch doctor of the Tree Kingdom in an effort to get to a stash of diamonds. He's stopped by Ka'anga.
Zwei, August: Scoop Comics (Chessler).A criminal on death row, Zwei has the strength and stamina of two men. He escapes and re-unites with his gang in order to go after space hero Dan Hastings whom he wants to not just kill but to torture to death. Even a bullet to the back (from his old girl-friend) doesn't put him out of commission. Hastings finally defeats him by gassing him.
Zzed: Airboy (Hillman). An old madman who seems to always be on hand during disasters. He seeks to destroy the world for that is when he believes he will die. He's frequently stopped by Airboy. In addition to his seeming immortality, he is shown to have hypnotic abilities.