Small spoilers for the mood of the book
The Zodiac comparison isn't really apt, as that's intensely focused on the mystery, whilst this one isn't really concerned with it. The characters are concerned with it, but it's never really a priority of the book to tie things together and wrap things up. Thank God.
The in's and out's of the mystery are so convoluted and twisted that figuring it out really plays second fiddle to everything else. The details of the mystery is sorta being dragged like a tail behind Sportello, and both we (at least I) and him only manage to keep the most recent details of it in our heads. But in a reductive "you can never really figure out the truth"-message-y way, then I guess this and Zodiac use mystery movie tropes to sort of a similar end. But other than that I can't really see too many similarities. Same time-period, yes, but completely different environments.