sentences:  Following his ministerial career, Zijlstra returned to the Vrije Universiteit as professor of public finance, though he also served between 1963 and 1966 as a member of the Senate.In 1973 Zijlstra became member of the Royal Netherlands Academy of Arts and Sciences.After the fall of the Cabinet Cals, Zijlstra headed an interim government as Prime Minister of the Netherlands and Minister of Finance between 22 November 1966 until 5 April 1967.