

It’s not clear to what extent the Zodiac Killer is multiple people, including hoaxers or copycat killers.
However, one thing that did happen was ciphers being sent into newspapers by some person, and IIRC some were solved, so if what you’re asking is “did the person involved have any familiarity with ciphers at all”, the answer is that he did. I don’t think that that would make him a “savant”, but he wasn’t simply sending in nonsense and claiming that it was enciphered text.
EDIT: Wikipedia’s bit on the enciphered letters:



TinEye turns up these results, with the first results from 2014.
https://tineye.com/search/0054c0fd20d1afef39480fca372bfa07ee632276?sort=crawl_date&order=asc&page=1
It looks like some of the early images had some text on them:
EDIT: That domain (“890801.net”) has lapsed in registration, but using archive.org’s Wayback Machine to look at that website in 2014, it has an image with similar text visible:
https://web.archive.org/web/20141216185019/http://890801.net/
EDIT2: Searching for “890801 halo” turns up this YouTube channel, which looks to also have the same content.
https://www.youtube.com/watch?v=rZr5Q4e4pqg
That has Korean-alphabet subtitles, so I’m assuming that it was some sort of Korean girl band from a decade and a half ago.
EDIT3: I won’t dig further, but I’d guess that that’s probably enough information for you to research further if you’re interested.
EDIT4: I lied. One last data point. The YouTube description mentions that this is a “Girl’s Generation” song, and some of the comments have users raving about some “Tiffany”. Assuming that that is actually “Girl’s Generation”, a Korean girl’s band, and not some later Korean girl’s band doing a cover of one of their stuff, one of their members is in fact also named “Tiffany”, so the girl in question might be a member of that band:
https://en.wikipedia.org/wiki/Girls'_Generation