Complex sentence: Higgins retaliated by claiming that players from Johnson's era had struggled to make breaks of 30 or 40 on tables with much larger pockets, and by calling Johnson one of the sport's worst commentators.
Split into simpler sentences: Higgins retaliated by claiming that players from Johnson's era had struggled to make breaks of 30 or 40 on tables with much larger pockets. Higgins also called Johnson one of the sport's worst commentators.