Complex sentence: Thomas left Platinum in early 1997 and spent the next two years producing and co-writing Brian Wilson's "Imagination" for Irving Azoff's Giant record label, as well as served as musical director, co-producer and promoter of Wilson's first world tour.
Split into simpler sentences: Thomas left Platinum in early 1997 and began producing and co-writing Brian Wilson's "Imagination" for Irving Azoff's Giant record label. He also served as musical director, co-producer and promoter of Wilson's first world tour.