Complex sentence: He was the WBC world heavyweight champion from 1977 to 1978 and is best known for his trilogy with Muhammad Ali, in which he defeated Ali in their first bout by split decision over twelve rounds in March 1973.
Split into simpler sentences: He was the WBC world heavyweight champion from 1977 to 1978. Norton is best known for his classic fight trilogy with Muhammad Ali, in which he defeated Ali in their first bout by split decision over twelve rounds in March 1973.