Complex sentence: He ended his season with seven wins out of his ten starts and racing at age four and five, won another six of ten starts while setting a track record in his win in the 1940 Massachusetts Handicap.
Split into simpler sentences: He ended his season with seven wins out of his ten starts. Racing at age four and five, he won six of ten starts while setting a track record in his win in the 1940 Massachusetts Handicap.