Soon after receiving her Ph.D., she undertook a training fellowship in the NIH laboratory of Christian B. Anfinsen,[4] who had won the 1972 Nobel Prize in Chemistry.

[5] It was here, in the Anfinsen-led Laboratory of Chemical Biology, that she initiated her studies on interferon, a large class of proteins called cytokines used for communication between cells to trigger the protective defenses of the immune system.

In 1979 and 1980 she and her colleagues were the first to report the complete purification and partial characterization, including the terminal amino acid sequence analysis, of a human interferon alpha.

[8] Following her NIH fellowship, Zoon moved to the FDA CBER in 1980 to continue her research on interferon; and, from 1992 to 2002, she served as CBER's director, focusing on developing policies to facilitate the development of biotechnology products, helped to advance the approval of a number of vaccines, and worked to achieve a safer blood supply.

Zoon also continues her laboratory research on structure and function of human interferons as chief of NIAID's Cytokine Biology Section.