Complex sentence: In 1991, Zelikow left the NSC to go to Harvard University, where from 1991 to 1998 he was Associate Professor of Public Policy and co-director of Harvard's Intelligence and Policy Program, in Harvard's Kennedy School of Government.
Split into simpler sentences: In 1991, Zelikow left the NSC to go to Harvard University. From 1991 to 1998 he was Associate Professor of Public Policy and co-director of Harvard's Intelligence and Policy Program, at Harvard's Kennedy School of Government.