[giblfiz]

Yep, which is actually specifically what tornado.cash was. It was a zk based mixer.

As you say: You absolutely CAN seamlessly mix crypto, but it will show a point in it's history where it says "this is where the crypto was seamlessly mixed"

[chrisco255]

That's only because tornado cash was a single contract and was mixing ERC20s that were not issued under a zk protocol. If you control the whole banana via a rollup or layer 1, absolutely, you can achieve complete privacy.