Self correction: my hype of Zcash’s superiority over Tor was unfounded. I forgot that Zcash is still on a public blockchain, subject in the future to advanced retrospective analysis by any party with a bit of money to partially decrypt it, such as quantum in the future (or who knows, even fully decrypt if it’s really far future with enough qubits).
And even before quantum arrives, Zcash’s blockchain data is already subject to passive timing attacks (i.e. analysing the blockchain). It’s easy for a shielded ZEC user to have bad or lazy OPSEC which makes their transactions easily linkable - something Zcash can’t possibly help with apart from community education (similar to how Tor project can’t help if someone reveals their real identity while on Tor).
Tor has an advantageous aspect in not having a public blockchain: only global passive adversaries (along with anyone they share that data with like other government agencies or people in power) could possibly emulate such an equivalent to blockchain graphs. They would have to have all or most of the Internet’s traffic (or just that known to be Tor-related) mapped out, which is vastly more data than Zcash’s ~34 GB so far. But apparently HDD storage is cheap, and NSA’s Utah data centre is plausibly conjectured to be intended for permanent storage of certain massive datasets considered worth keeping for later timing analysis and/or direct quantum decryption (normally NSA throws away most of what they collect away after a week etc.). So to at least one adversary out there, probably Tor is still just as problematic as a privacy coin blockchain. However, not everyone has that adversary, and nasty data brokers can analyse Zcash, but not Tor traffic, so Tor remains mighty against most attackers.
Zcash itself (no matter how much you self-churn) has two data realms I know of so far: the permanent public blockchain, and then the transient, real-time, p2p network data privately collectable by some nodes, some of the time.
So: Zcash and Tor aren’t that directly comparable. In the end, balancing all threat models, perhaps both are kind of on par with each other. But I compared an apple to an orange.
(This means Monero combines the worst elements of Zcash and Tor’s respective weaknesses: a permanent public blockchain, AND Tor’s level of quantum vulnerability. It’s a distant third place. Poor Monero.)