Complex sentence: In 1583 he settled in Haarlem, Holland, where he worked for 20 years on a commission by the city fathers to inventory "their" art collection; work that he later published in his "Schilder-boeck" (Painter's Book).
Split into simpler sentences: In 1583 he settled in Haarlem, Holland, where he worked for 20 years on a commission by the city fathers to inventory "their" art collection. He used this work in his "Schilder-boeck" (Painter's Book).