Complex sentence: Billy earned the nicknames "Last-Race Cookie" following his riding of the winner in the last race 13 Saturday's in succession in Sydney and also "The Champ" due to his exquisite riding skills.
Split into simpler sentences: Billy earned the nickname "Last-Race Cookie" following his riding of the winner in the last race 13 Saturdays in succession in Sydney. He was also known as "The Champ", due to his exquisite riding skills.