Decades before the infant Kal-El arrived on Pre-Crisis Earth-1, Black Zero was employed by the Interstellar Pirate Empire to destroy Krypton as he apparently had other worlds on the empire's behalf. Black Zero observed Jor-El warning the Kryptonian Science Council of the planet's impending destruction. However, Black Zero's instruments discovered that Jor-El's calculations had been mistaken and Krypton would be spared. Using a "ground-boring rocket," Black Zero exacerbated the chain-reaction caused by a massive uranium deposit under Krypton's surface in order to destroy the planet.
Superman was made aware of Black Zero's existence after being summoned to the headquarters of the Central Intelligence Agency before a meeting of U.S. law enforcement agency personnel, as well as Chief Inspector Watkins of Scotland Yard. Black Zero was described to Superman as having purple eyes, a forked tongue, and no fingerprints, leading them to the conclusion that he was of extraterrestrial origin. The assembly proceeded to explain this information, as well as knowledge of Black Zero's plan to destroy all life on Earth, had been gathered by the unfortunate Agent 009, who had been discovered and killed. The meeting abruptly ended when Superman was attacked by two enormous flaming hands, distracting him from the appearance of a challenging message. Superman took Chief Inspector Watkins with him and left in pursuit of Black Zero.
Superman took Watkins to the Fortress of Solitude, where his computer identified Watkins as a disguised Black Zero. Black Zero revealed to Superman his connection to Krypton and escaped the Fortress of Solitude before the Man of Steel could stop him. Jax-Ur, the Kryptonian criminal confined to Phantom Zone, telepathically contacted Superman, wanting to assist him in avenging Krypton against Black Zero. Superman agreed, using the Phantom Zone Projector to restore Jax-Ur.
The unlikely duo thwarted Black Zero's attempt to similarly destroy the Earth. Using Red Kryptonite, Jax-Ur assumed a Medusa-like form and turned the alien saboteur into stone. He then smashed Black Zero's stone body, killing him and avenging Krypton.