Background: Robert Dennis Crumb (; born August 30, 1943) is an American cartoonist and musician who often signs his work R. Crumb. His work displays a nostalgia for American folk culture of the late 19th and early 20th centuries, and satire of contemporary American culture. Crumb is a prolific artist and contributed to many of the seminal works of the underground comix movement in the 1960s, including being a founder of the first successful underground comix publication, Zap Comix, contributing to all 16 issues. He was additionally contributing to the East Village Other and many other publications, including a variety of one-off and anthology comics.
Context: In January 1967 Crumb came across two friends in a bar who were about to leave for San Francisco; Crumb was interested in the work of San Francisco-based psychedelic poster artists, and on a whim asked if he could join them. There, he contributed upbeat LSD-inspired countercultural work to underground newspapers. The work was popular, and Crumb was flooded with requests, including to illustrate a full issue of Philadelphia's Yarrowstalks.  Independent publisher Don Donahue invited Crumb to make a comic book; Crumb drew up two issues of Zap Comix, and Donahue published the first in February 1968 under the publisher name Apex Novelties. Crumb had difficulty at first finding retailers who would stock it, and at first his wife took to selling the first run herself out of a baby carriage.  Crumb met cartoonist S. Clay Wilson, an art school graduate who saw himself as a rebel against middle-class American values and whose comics were violent and grotesque. Wilson's attitude inspired Crumb to give up the idea of the cartoonist-as-entertainer and to focus on comics as open, uncensored self-expression; in particular, his work soon became sexually explicit, as in the pornographic Snatch he and Wilson produced late in 1968.  The second issue of Zap appeared in June with contributions from Wilson and poster artists Victor Moscoso and Rick Griffin. In December, Donahue published the still-unreleased issue as #0 and a new third issue with Gilbert Shelton joining the roster of regulars. Zap was financially successful, and developed a market for underground comix.  Crumb was a prolific cartoonist in the late 1960s and early 1970s; at his peak point of output he produced 320 pages over two years. He produced much of his best-known work then, including his Keep on Truckin' strip, and strips featuring characters such as the bohemian Fritz the Cat, spiritual guru Mr. Natural, and oversexed African-American stereotype Angelfood McSpade. During this period, he launched a series of solo titles, including Despair, Uneeda (both published by Print Mint in 1969), Big Ass Comics, R. Crumb's Comics and Stories, Motor City Comics (all published by Rip Off Press in 1969), Home Grown Funnies (Kitchen Sink Press, 1971) and Hytone Comix (Apex Novelties, 1971), in addition to founding the pornographic anthologies Jiz and Snatch (both Apex Novelties, 1969).
Question: What about the underground comix?. Whats the answer?
Zap was financially successful, and developed a market for underground comix.