I had a great idea that someone else might want to pursue. I finally found a website/app that can compare two documents to see if they were written by the same author. This might be able to test some of the major candidates – those with known public writings.
This is the website:
My idea is to create a document containing the identified Zodiac letters. Then create separate documents containing known writings for each Manalli, Kaczynski, Gaikowski, and whomever else applies. Then run a comparison for each to the Z file and see if there is a match.
I read somewhere that you might need 5,000 words things to work on the site. But I don’t know if you need 5,000 words in both documents or only in one of the two documents. You might be able to have 1 5,000 word document that you can compare to a 300 word document. I also don’t know if you actually need 5,000 words. it might work with fewer. I’m new to this.
I started to do it myself. But then I decided I didn’t really want to submit a document with a bunch of creepy letters to a website. So perhaps someone with a braver soul or a longer track record of true crime investigation would be a better candidate.
These letters are quite well known, I don’t think you’d be confused with a random maniac using them on such a website 
