I don’t think the Zcash support is there yet. The issue was never commented on: Add Zcash shielded z-address support · Issue #4941 · bisq-network/bisq · GitHub
There was recent discussion about adding researching stablecoins on Zcash, which might also help.
I think there is another way out of this which is via bridging. I have understood that some of the work started with ZSAs means we can start having support for bridged assets, thus enabling (trusted) two-way bridges to operate. We would still need to have someone build this though.
Additionally, there is work being done such as the ZEC.d bridge which would allow offramping via AVAX.
All in all its clearly a huge problem, and we should have multiple projects this issue.