Which info does zkSNACKs collect from customers in Wasabi wallet? I'd like to sort misinformations from facts.
None, but that isn't the point. The point is that funding surveillance firm to spy their users is malicious, especially when portraying yourself as the ultimate privacy and fungibility solution. It's pure hypocrisy.
You've said zkSNACKs doesn't leak data doesn't know any thing about it's users so what's zkSNACKs going to do when Coinfirm reject a mix?
They're probably going to be okay with it, and approve the rejection (if there's approval part from the coinjoin server, we don't know for sure*). According to this policy, though, don't expect to question them for anything:
https://raw.githubusercontent.com/zkSNACKs/WalletWasabi/master/WalletWasabi/Legal/Assets/LegalDocumentsWw2.txt (Coin filtering part)
* From what I saw in the unit tests, the coordinator software makes a request to the chain analysis firm, and rejects anything without approving it.