Complex sentence: His time in charge was one of the clubs most successful eras as, under his guidance, the club won the league nine times; this included a five-in-a-row sequence (1961--65) and another three consecutive.
Split into simpler sentences: His time in charge was one of the clubs most successful eras as, under his guidance, the club won the league nine times. This included a five in a row sequence (1961--65) and another three consecutive.