Zimmerman began her career with the Department of Revenue in 2001 in the Bureau of Human Resources, where she was responsible for training and employee development activities. She later transitioned from Human Resources to serve as the Training Lead for the department's Business Tax System implementation and held that role until she took on a new position when PRISM was formed. She served as the Chief of the Strategic Planning and Performance Division in PRISM prior to being named the bureau's director in 2021. In recent years, Zimmerman has led many employee engagement initiatives, including the weekly leadership podcast workshop, and served on the Department's Human Diversity, Equity, and Inclusion (DEI) Core Team.

In her role as Deputy Secretary for Administration, Zimmerman has oversight of the Bureaus of Administrative Services, Fiscal Management, Imaging and Document Management, and PRISM. Her responsibilities include overseeing the department's budget, digital document management and remittance processing services, administrative support services and mailing operations, strategic, risk, and project management functions, and employee development. She is the executive sponsor for the agency's DEI initiatives and serves as the Secretary of Revenue's designee for the Pennsylvania Gaming Control Board (PGCB), due to the Secretary's position as an ex-officio member of PGCB.​