Complex sentence: Although Impressive raced for a short time after Landers sold him to Fennel Brown, he was quickly excluded from any performance discipline due to pedal osteitis, leaving halter as his only choice, and his groundbreaking 1974 World Championship soon cemented his role in that discipline.
Split into simpler sentences: Although Impressive raced for a short time after Landers sold him to Fennel Brown, he was quickly excluded from any performance discipline due to pedal osteitis, leaving halter as his only choice. His groundbreaking 1974 World Championship soon cemented his role in that discipline.