Complex sentence: Her wins included the classic 1000 Guineas at Newmarket, the Nassau Stakes and the Yorkshire Oaks against her own age and sex but more notable were her successes in open competition including the Goodwood and Doncaster Cups and three of the seasons most valuable handicap races.
Split into simpler sentences: Her wins included the classic 1000 Guineas at Newmarket, the Nassau Stakes and the Yorkshire Oaks against her own age and sex. More notable were her successes in open competition, including the Goodwood and Doncaster Cups and three of the seasons most valuable handicap races.