Ron is known for his work on Silver Surfer and Green Lantern, as well as the DC vs. Marvel crossover and Batman/Aliens. He co-created most notably Green Lantern Kyle Rayner and Genis-Vell in Silver Surfer Annual #6. Marz worked on the CrossGen Comics series Scion, Mystic, Sojourn, and The Path. At Dark Horse Comics he created Samurai: Heaven and Earth and various Star Wars comics. He has written for Devil's Due Publishing's Aftermath line including Blade of Kumori. In 1995, he had a brief run on X-O Manowar for Valiant Comics. The following year, Marz wrote the DC/Marvel: All Access limited series which was an intercompany crossover between DC and Marvel characters.
While writing Green Lantern, Marz wrote the "Emerald Twilight" storyline, in which the character of Hal Jordan, stricken with grief, became a mass murderer, leading to the destruction of the Green Lantern Corps, and Kyle Rayner being chosen at random as the last Green Lantern.
In 2020 Marz collaborated with Andy Lanning on the nine-issue DC Comics crossover storyline "Endless Winter", which would debut that December