Complex sentence: WCBS-FM was never successful with its rock format, competing with stations such as WPLJ (the other former WABC-FM) and WNEW-FM had most of the rock audience.
Split into simpler sentences: WCBS-FM was never successful with its rock format. Competing stations such as WPLJ (the other former WABC-FM) and WNEW-FM had most of the rock audience.