Complex sentence: Sercu is the record holder for the number of six-day track race victories, having won 88 events out of 223 starts between 1961 and 1983; several of these wins were with cycling great Eddy Merckx.
Split into simpler sentences: Sercu is the record holder for the number of six-day track race victories, having won 88 events out of 223 starts. Several of these wins were with cycling great Eddy Merckx.