Mr. Zarella will rejoin his former employer, Bausch & Lomb, Rochester, N.Y., as chairman-CEO.
Mr. Zarella, 52, arrived at GM in late 1994 as group vice president of sales, service and marketing with much fanfare as a rare industry outsider to oversee the auto giant's reorganization of brand management.
Mr. Zarella in a conference call today said GM "didn't move fast enough" in "a lot of what we've done," including pushing into the truck market.
Bob Lutz, the former industry veteran who had spent time at all of Detroit's Big Three automakers, took over Mr. Zarella's product duties. Mr. Lutz, who came to GM in September as vice chairman of product development, was promoted today to chairman of North America.