Original: His two most financially successful films were released in 1974: Blazing Saddles (co-written with Richard Pryor, Andrew Bergman, Norman Steinberg and Alan Uger), and Young Frankenstein (co-written with Gene Wilder).
Simplified: Two of his most popular films are Young Frankenstein (co-written with Gene Wilder) and Blazing Saddles (co-written with Richard Pryor).