Seriously though, I don't think the Zodiac case could translate well into video games because it was very drawn out in time and range, and its main point of interest is mostly the bizarre correspondence.
Jack the Ripper works so well because it's localized in London, already a prime vidya setting, and had a shocking killing method. Zodiac was over quite a wide range, especially if you include the less definite cases. Not much about it screams action game, so that leaves you with a standard murder mystery adventure game in a setting without a whole lot of interesting locales. Maybe it could include a focus on the letters with graphology and cryptology and shit, I don't know.
Long story short, video games benefit from tight design and I don't see a Zodiac killer game permitting much of that. It could however be an analog in a fictional city about a fictional but similar case.
Bizarre single murders could be more the ticket. The Dyatlov Pass Incident comes to mind. I know there was Kholat, supposedly, but I didn't like it overmuch and quickly refunded it, so I don't even know if it used the case well.