[1] Zijlstra was on the sixth position of the candidate list of the Party for Freedom at the 2009 European Parliament election.

He went on to serve as a parliamentary aide to the Party for Freedom group in the European Parliament from September 2010 onwards.

On 13 September 2011 he replaced Daniël van der Stoep, who gave his seat back to the Party for Freedom after being involved in a drunk driving incident in August 2011.

[3] In March 2012 the Party for Freedom launched a website on which Dutch citizens could complain of inconveniences caused by migrant workers from Central and Eastern Europe.

Zijlstra defended the speech in the European Parliament, citing that the party listens to the complaints by the population.

Zijlstra had been member, amongst others, of the Committee on Civil Liberties, Justice and Home Affairs and the Delegation for relations with the Palestinian Legislative Council.