Cryptonym: ZR
This routing sheet from 1962, related to another defector returned from the Soviet Union named Robert Webster, has a handwritten note saying "pls ZR Webster." Please wiretap him?
1993.06.22.16:59:56:210380: ALLEGATION OF A. EDWARD HORSEY THAT ONE AL GROAT WAS INVOLVED IN ASSAS
In a similar vein to the previous source, this one has a handwritten note to "ZR Ruby," referring to Jack Ruby. The note specifically references paragraph 3 of the enclosed FBI memo, which refers to the theory that Ruby had killed Oswald under a post-hypnotic suggestion. But since Ruby was already dead by this point, "ZR Ruby" can't refer either to wiretapping or hypnotizing him. Instead, it likely means reviewing previously-collected wiretaps.
State Secret, Chapter 1, by Bill Simpich
The above sources come from chapter 1 of Bill Simpich's State Secret. Scroll down to the section whose title begins "After the downing of the U-2..."
Peter Dale Scott, Oswald, Mexico and Deep Politics, p. 18.
"The ZR cryptonyms...were normally assigned to CIA radio monitoring projects collecting data for the NSA."
Bayard Stockton, Flawed Patriot, found at http://jfkcountercoup.blogspot.com/2012/05/americas-james-bond-at-jmwave.html
"ZR was a digraph for Division D, Cryptological Procurement. It seems to have served purposely to confuse the Castro hit ops with Earl Harter’s closely held series of operations to procure cryptographic materials by breaking-and-entering target premises. Very few, even in D., knew what Harter’s boys did;….Precisely because Division D was so secure and already involved in matters gentlemen preferred not to know about, it was the logical administrative compartment in which to house CIA’s newest and touchiest activity, the projected assassination of political leaders whose further existence impinged on U.S. interests…"
Peter Dale Scott, Oswald, Mexico and Deep Politics (2013), found at https://books.google.com/books?id=98ctAgAAQBAJ&printsec=frontcover&dq=oswald+mexico+and+deep+politics&hl=en&sa=X&ved=0ahUKEwjYycmO4M_SAhUT0WMKHaDvDv8Q6AEIHDAA#v=onepage&q=zr%2Fbeach&f=false
"The ZR cryptonyms were normally assigned to CIA radio monitoring project collecting data for the NSA (Agee, 348, 351, etc.)
104-10224-10000: LYNCH, GRAYSON L., OP.
In the ZRJEWEL cryptonym, the ZR changed in the sixties to IU.