A dentistry graduate, she subsequently did her doctorate, underwent further orthodontic training and qualified as a dentist at the Free University of Berlin. She then went on a study visit to the United States, where she participated in an orthodontics programme at a New York university clinic.
Having worked as an assistant in a Berlin orthodontic surgery, she set up her own practice, maintaining close contact with university experts and engaging in research activities. Since September 1995 she has been qualified to provide further training, her authorisation to do so having been regularly reviewed, most recently in November 2008.
She has been a member of the Advisory Board of the Berlin and Brandenburg Orthodontic Society (Gesellschaft für Kieferorthopädie von Berlin und Brandenburg e.V.) since 1997 and its vice-chair since 2003. She has worked for the Board of Examiners of the Berlin Dental Chamber since September 2004. Dr. Zellmann has three children between the ages of seven and eleven. She is fluent in English.