In 1973, Zien made his television debut on an episode of Love, American Style. More guest roles in television followed, and in the early 1980s, he began a stream of regular TV roles. In 1981, he appeared on Ryan's Hope as Daniel Thorne, the Producer of the fictional Proud and the Passionate soap opera on the series in which major character Kimberly Harris (Kelli Maroney) was starring on. Later that year, he began a two-year run in the freshman NBC sitcom Love, Sidney as Jason Stoller, the young, hot-shot ad agency Director who was Sidney Shorr's (Tony Randall) boss. Immediately after Love, Sidney's cancellation, Zien was cast in a similar role on the ABC sitcom Reggie, an American adaptation of the British series The Fall and Rise of Reginald Perrin. He played C.J. Wilcox, the overbearing young boss of Richard Mulligan's Reggie Potter. The series aired as a summer replacement during August and September of 1983, but was not renewed by ABC after the tryout run. Zien later starred on the short-lived CBS drama Shell Game in 1987.