Complex sentence: Liu had served on the New York City Council representing District 20, and was elected to the City Council in 2001 to represent northeast Queens, then was re-elected in 2003 and 2005.
Split into simpler sentences: Liu had served on the New York City Council representing District 20. He was elected to the City Council in 2001 to represent northeast Queens, and was re-elected in 2003 and 2005.