Zap Comix #0 was published in the latter half of 1968, sometime between a few weeks and a few months after Zap Comix #2 was published in August. But if not for the fact that Brian Zahn (publisher of Yarrowstalks) had kept Crumb's artwork for Zap #0 when he traveled to India in 1968, this would have been the first book in the Zap Comix series. If it had been, would Zap Comix #0 have made the same impact that Zap #1 did when it was published? In all likelihood, yes, it would. But it would've been just a little more dicey.
Though still revolutionary for a comic book in 1968, Zap #0 is not quite as controversial as Zap #1, but it does get progressively more outrageous as you get deeper into the book. The inside front cover features Robert Crumb (as "Mr. Sketchum") introducing "Zap Comics" as "Audacious! Irreverent! Provocative!" But the first story, "Meatballs," is about as provocative as a good Mad magazine story of the same era. Sure, there's a "beatnik who was always high" in three panels, but even Mad would be bold enough to do that.-- Comixjoint