Zaagsma was a researcher in the Public History Research and Consultancy Center, Faculty of Arts, University of Groningen, The Netherlands. He held a postdoctoral position at the Department of Hebrew and Jewish Studies, University College London and subsequently worked as editor & web developer at the Huygens Institute for the History of the Netherlands (Netherlands Academy of Arts and Sciences). Before joining the University of Luxembourg he was a Research Fellow at the Lichtenberg Kolleg, The Göttingen Institute of Advanced Study, University of Göttingen.