Complex sentence: Clark then stepped down from performing to turn his attention to writing and producing for other artists, such as Natalie Imbruglia (co-writing with her most of her second album "White Lilies Island"), Liz Phair, Nick Carter, Ashley Parker Angel, k.d.
Split into simpler sentences: Clark then stepped down from performing to turn his attention to writing and producing for other artists. He has also worked as a songwriter or producer for Liz Phair, Nick Carter, Ashley Parker Angel, k.d.