As president of the Hoboken City Council, she became acting mayor after incumbent Peter Cammarano's resignation on July 31, 2009 following his arrest on corruption charges.

She also served as a board member of the Kaplan Cooperative Preschool and as secretary of the Parent Teacher Student Organization for the Elysian Charter School.

[7][8] In October 2007, Zimmer, as Hoboken's 4th Ward Councilwoman, supported a voter referendum to create an Open Space Trust Fund.

[12] On July 23, 2009, Cammarano was arrested by the FBI as part of a major corruption and international money laundering conspiracy probe known as Operation Bid Rig.

In the special election, Zimmer faced six opponents: City Councilwoman Beth Mason, businessman Frank Raia, former Hoboken Municipal Court judge Kimberly Glatt, Hoboken Republican Club co-founder Nathan Brinkman, management consultant Everton A. Wilson, and former corrections officer Patricia Waiters.

On September 9, 2013, she was recognized as "Hero of the Harbor" by the Waterfront Alliance for her work "to make her city a national model for preparedness, meeting with FEMA and state officials, urban planners, scientists and many others to create an 'integrated solution.

[32][33][34] Zimmer has been a strong proponent of same-sex marriage and publicly urged Governor Christie to change his position in opposition.

[36] In May 2010 Zimmer invited Governor Christie to speak in Hoboken in his first of a series of town hall meetings throughout the state supporting the 2% tax levy cap.

[39][40] On January 18, 2014, Zimmer appeared on Up with Steve Kornacki,[41] and said that Lieutenant Governor Kim Guadagno and Commissioner of the New Jersey Department of Community Affairs Rich Constable had pressured her to support a Rockefeller Group development project in Hoboken in exchange for the city receiving additional federal Sandy relief aid.

[43] Following her television appearances, the Federal Bureau of Investigation and United States Attorney for the District of New Jersey met with Zimmer.

Zimmer stated: "As their investigation proceeds, they have asked me to refrain from giving any additional interviews and I am respecting their request.

"[54][55][56][57] Zimmer said she had not come forward until after the so-called Bridgegate scandal (which had become public knowledge 10 days earlier) because she thought her claims would be not taken seriously.

[59][60] In April 2014 the Hoboken City Council adopted a resolution which allowed the attorney handling the matter to waive attorney–client privilege, enabling him to speak to the U.S.

[61] An internal investigative was commissioned by the Christie administration and conducted by Randy Mastro of law firm Gibson, Dunn and Crutcher.

"[65][66] In editorials, The Star-Ledger and The New York Times labeled the report a "whitewash"[67][68] as did 56% of New Jersey voters in an April 2014 survey by the Quinnipiac University Polling Institute.

[70] In letters dated May 1, 2015 to Guadagno, Constable and Ferzan the U.S. Attorney wrote: "Based on the evidence developed during the investigation and our review of applicable law, we have concluded that no further action is warranted in this matter.

[74] In 2015, various news articles pointed to documents showing a partnership with her spouse as an influential figure in her administration and Hoboken City government affairs.