In 1999, Ze'ev was elected to the Knesset on the Shas list, and was re-elected in 2003, 2006, 2009, and 2013. During his time in the Knesset, he served as a member of the Knesset Committee, the Foreign Affairs and Defense Committee, the Constitution, Law, and Justice Committee, and the Committee on Interior Affairs. In the 17th Knesset (2006–2009), he served as chairman of the Knesset Committee on the War Against Drugs and Alcohol, coordinating with all the relevant agencies and holding many meetings which led to a body of legislation to fight drug and alcohol abuse.