Zerocash is an academic paper and early implementation from a group of researchers -- a proof of concept of using zero-knowledge proofs to add privacy to a public blockchain ledger.

Zcash is the ongoing project based on Zerocash, started in large part by those same researchers, but with funded teams of engineers continuously iterating on the protocol and implementations.

It certainly counts as progress. The main criticism to Zcash used to be that 90%+ of the transactions were transparent.

Zcash seems interesting to me in that it feels like Bitcoin without either ossification or getting overwhelmed into becoming a casino substrate like programmable currencies. It evolves but slowly and in a particular well scoped direction.