A fragmented cipher was included with a brief note sent out in early December 1969. It consisted of 38 letters and symbols, all of which appeared in the Z340.

The above image of the letter is taken from Richard Grinell’s blog-post “Can the 2020 Codebreakers Crack This?”. Published 10/13/21, on his website Zodiacciphers.com. Richard points out the shared symbols coming from the Z340, and assigns them plaintext from the Oranchak et al solution. As he explains, the use of the end pieces from the 340 makes it likely this letter is the real Z deal. Inspired me to solve it for myself. I wanted to see what Zodiac was on about so soon after the Z340 was sent. Assuming as I do that the FBI solved 340 right away, with instructions that this was part of a CIA/mob operation, not to be interfered with, what did the Z38 here intend to further tip off?
There hadn’t been enough time to assign the symbols new values. That’s what the use of the beginning and end pieces of the 340 would have told the FBI cryptographers and J. Edgar Hoover.
So without much further ado let’s plug in plaintext from my own Z340 solution, straight substitution style. ( I believe both 340 solutions are valid…there is a way that it can be done).

First line then is about the author, George Achilles Karadanis. He gives details of his birth here but still chooses to remain rather anonymous. I interpret it to read: I traveled in a boat (to) N for Natick, Massachusetts, his place of birth. His mother must have been pregnant, or have become so, on the boat on the way from Anatolia, Turkey.
Second line indicates that EE, or Zeen, Xenophon Lusby Anthony, has stopped being part of the group. Thanks to public reaction, CIA operations involving the American people were about to be shut down in 1970. The message here being Zeen is following instructions to stop his participation.
In the third line, Karadanis is saying for the record, that Zeen, Mr. Spy guy, OO7, is a RAT, and needs to have his mouth shut, perhaps, by the FBI. He is reiterating the bitter messages about Xenophon Anthony found in the 340. Soon after remember Zeen was fingerprinted by FBI agaents and then let off the hook.
Fourth line hints at another victim to follow. The RN mentioned in my 340 solution? Donna Lass? N.N.N. could stand for something like “naughty naughty nurse”. H would stand for Hospital, referring to the S.F. Presidio Hospital, where she was still working at that time. The double O with the dots here indicates breasts: it’s a woman, duh. It also stands for “oh oh!”, she is in danger from someone.
That person is “E. B. NY Euro”. This is Lawrence Kane, who sometimes signs his name Barton, for his first wife Eileen Barton (E. B.), and yes he is a ‘NY Euro’: Kane being the 3rd member of the group, the mob guy, and the one who named the group: ‘Zodiac’.