Zion graduated from the University of Pennsylvania and Yale Law School, working as a trial lawyer until becoming Assistant US Attorney for New Jersey in 1961.

In 1971, Zion revealed that Daniel Ellsberg was the source of the Pentagon Papers, the classified study on the history of United States' political and military involvement in Vietnam from 1945 to 1967.

Zion, who was not affiliated with any news organization at the time, made the revelation on a popular New York City radio show.

Many journalists regarded his disclosure of Ellsberg's identity as a breach of professional ethics, and Zion said he was considered a "pariah" by journalism colleagues for several years afterward.

Her death and the subsequent investigation and trial led to improvements in hospital residents' working conditions.