Complex sentence: They remained competitive throughout the remainder of the 60s and on into the early 70s when they broke through to the top flight on the strength of a Regionalliga West title and victory in the subsequent Bundesliga promotion playoffs in 1972.
Split into simpler sentences: They remained competitive throughout the remainder of the 60s and on into the early 70s. They broke through to the top flight on the strength of a Regionalliga West title and victory in the subsequent Bundesliga promotion playoffs in 1972.