Complex sentence: Returning to academia, he taught as visiting professor at Heidelberg University, Columbia University, and the University of Pennsylvania during the 1960s, before serving as Vice-Chancellor of Dhaka University from 1960 to 1963, and of Karachi University from 1971 until his death in 1975.
Split into simpler sentences: Returning to academia, Hussain taught as visiting professor at Heidelberg University, Columbia University, and the University of Pennsylvania during the 1960s. He served as Vice-Chancellor of Dhaka University from 1960 to 1963, and of Karachi University from 1971 until his death in 1975.