Complex sentence: Between 1970 and 1975, he had already been a student at Santa Monica College and at the University of California Los Angeles, where he had completed 88 credits of class work yet had been unable to complete his degree because of promotional tours and his film career.
Split into simpler sentences: Between 1970 and 1975, he had already been a student at Santa Monica College and at the University of California Los Angeles. At these California campuses, he had completed 88 credits of class work yet had been unable to complete his degree because of promotional tours and his film career.