This issue is a variant of Zap Comix (Apex Novelties, 1967 series) #6. There exist further variants.
Early printings by Print Mint. Later printings by Last Gasp.
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. 2nd print has 0.75 USD cover. 3rd print has 1.00 USD cover.
4th print has 1.50 USD cover. 5th print has 2.50 USD cover (published by Last Gasp).
6th print has 2.95 USD cover. 7th print has 4.95 USD cover.
Jam session where the artists of the issue draw their own characters.
Image on back cover of issue.