Complex sentence: His comeback culminated at the 1994 US Open with a five-set fourth-round victory against compatriot Michael Chang, and then becoming the first man to capture the US Open as an unseeded player, beating Michael Stich in the final.
Split into simpler sentences: His comeback culminated at the 1994 US Open with a five-set fourth-round victory against compatriot Michael Chang. He then became the first man to capture the US Open as an unseeded player, beating Michael Stich in the final.