In 1964, Zwilich moved to New York to study composition with Roger Sessions and Elliott Carter, and violin with Ivan Galamian and Richard Burgin. She played with the American Symphony Orchestra under Leopold Stokowski from 1965 to 1972, where she acquired invaluable training in performance and orchestra. She did not begin attending Juilliard School until 1975, when her works first came to prominence after Pierre Boulez programmed her Symposium for Orchestra with the Juilliard Symphony Orchestra.

Zwilich is the first woman to hold a Doctorate in Composition at The Juilliard School.

Zwilich revolutionized the path for women in music in countless ways. During an era where relatively few women were winning honors and distinctions, much less being hired in professional orchestras, she created an impressive reputation for herself among her peers.

Sensitive to gender issues, Zwilich recalls a standard art book that "required heavy lifting for the number of artists represented, but completely lacking any female entries," and finds it interesting "how women were written out of the history, or erased from it."

However, she admits that she is not impeded by the general attitude toward women composers. She found that when someone put up an obstacle, another wanted to help her out.