Complex sentence: He trained his own Mount Sion club to many county victories in the 1950s and 1960s, however, it was as the trainer of the Waterford senior hurling team that he enjoyed an unprecedented run of success.
Split into simpler sentences: He trained his own Mount Sion club to many county victories in the 1950s and 1960s. However, it was as the trainer of the Waterford senior hurling team that he enjoyed an unprecedented run of success.