(1961) is a historian and theologian. The biography served as a dissertation in the humanities at the Amsterdam Free University in order to receive the degree of Ph.D. in 2018. Earlier, in 1995, Zeilstra earned the degree of Th.D. with his thesis European Unity in Ecumenical Thinking, 1937-1948, in the Theological Faculty at Utrecht University. His current job is as a Protestant minister in Hilversum.