On Joshua Lederberg's "Profiles in Science" NLM website, searching for "Esther Zimmer" returns the following PDF file. Esther Zimmer is mentioned in the first full paragraph on the second page.
Click to view PDF file referring to "Esther Zimmer",
not "Esther M. Lederberg".
Note: the file opens in a new instance of your browser.
This specific piece of correspondence may be found on Joshua
Lederberg's NLM website, identified as with the ID:
bbapby.
http://profiles.NLM.NIH.gov/BB/