When he was 17, in response to the dismissal of several popular teachers, Zimmerman took part in a demonstration in which protesters barricaded the building.

[1] The project was converted into a company, Designing Hong Kong Limited, founded by him together with Christine Loh, Peter Wong and Markus Shaw.

[3][4] He is currently the vice-chairman of the Coalition on Sustainable Tourism and Chairman of the Single-Use Beverage Packaging Working Group, best known for its initiative Drink Without Waste.

[4] In 2006, lawmakers Audrey Eu Yuet-mee, Albert Lai Kwong-tak and Ronny Tong Ka-wah asked Zimmerman to join the Civic Party as a founding member.

He later won a seat in Pokfulam in the Southern District Council in a by-election in 2010, succeeding Ronald Chan Ngok-pang who resigned after being hired by the Chief Executive's Office.

He gave up his Dutch citizenship but did not get enough nominations and subsequently endorsed another pro-democracy candidate Frederick Fung.

[5] In the 2016 Legislative Council election, Zimmerman ran in Hong Kong Island as an independent democrat.

[7] He joined 20 other electors (from the 1,194 total) in nominating former judge Woo Kwok-hing for Chief Executive in the small-circle 2017 election.

In the 2019 District Council election, Zimmerman successfully won his re-election bid in the Pokfulam constituency, with 2,547 votes.