This issue is a variant of Zap Comix (Apex Novelties, 1967 series) #4. There exist further variants.
Zap 4 went through a landmark obscenity trial, much legal information may be accessed. Early printings by Print Mint. Later printings by Last Gasp with the Apex Novelty logo on front cover.
Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
1st print has 0.50 USD cover. Has heavy stock cover.
2nd print has 0.50 USD cover. Has lighter cover stock, no copyright on inside front cover.
3rd print has 0.50 USD cover. Has 1969 copyright on inside front cover.
4th print has 0.75 USD cover. 5th print has 1.00 USD cover. 6th print has 2.00 USD cover.
7th print has 2.50 USD cover (published by Last Gasp). 8th print has 2.95 cover.
9th print has 3.95 USD cover (not listed in Fogel's guide). 10th print has 4.95 USD cover.
Wrap-around cover image.
Sequence can be read forward or backward.
Center spread is 2 page splash.
Jam sequence where the artists of the issue draw their own characters.