Complex sentence: West Coast were the dominant team during Fremantle's initial years, winning the first nine derbies, however since Fremantle won their first Western Derby in July 1999, it has been fourteen wins to eleven in Fremantle's favour.
Split into simpler sentences: West Coast were the dominant team during Fremantle's initial years, winning the first nine derbies. However since Fremantle won their first Western Derby in July 1999 it has been fourteen wins to eleven in Fremantle's favour.