Complex sentence: Harris was a co-producer for the television series "Sex and the City", for which she also wrote two episodes, and executive producer for the prequel "The Carrie Diaries", for which she also wrote the adaptation.
Split into simpler sentences: Harris was a co-producer for the television series "Sex and the City", for which she also wrote two episodes. She is an executive producer for the prequel "The Carrie Diaries", for which she is also writing the adaptation.