Complex sentence: From 1988 to 1990 the XXXX State Cup was contested by the combined Queensland Country team, but the winners of the XXXX Shield were the de facto Country champions between 1986 and 1991, as were the XXXX State Cup finalists from 1983 to 1985.
Split into simpler sentences: From 1988 to 1990 the XXXX State Cup was contested by the combined Queensland Country team. The winners of the XXXX Shield between 1986 and 1991 were the de facto Queensland Country champions, as were the XXXX State Cup finalists from 1983 to 1985.