[9] In 2014 he was leader of a commission set up by the Vrije Universiteit Amsterdam to look into the academic work of Peter Nijkamp after allegations of self-plagiarism.
[11] Zwemmer also worked as part-time tax judge at the Courts of Appeal of 's-Hertogenbosch, Arnhem and Amsterdam.
[12] While working as professor Zwemmer wrote around six fiscal opinions in the form of scientific analyses for tax advisors each year, after his retirement the number lowered to around four.
[17] Over a thirty-year period Zwemmer frequently voiced his opinion on fiscal matters in articles and columns.
He noted that the part-time professors only took part in academic life and responsibilities to a limited extend.
[2] In 2015 Zwemmer stated that Fred Teeven, whilst he was working for the Public Prosecution Service, was complicit in money laundering when he made a deal with criminal Cees H.[19] In the wake of the revealing of the Panama Papers in 2016 Zwemmer stated that the case could lead to an improved tax morale.
[20] In 2016, after previously secret documents were unvealed about a tax compensation for the House of Orange-Nassau, Zwemmer stated that it was highly unusual and not correct.