Three different ideas can get tangled together: the puzzle miners solve, the privacy a transaction can use, and the way a pool submits work across networks. They sit at different layers of the system.
Mining · Equihash
Miners search for valid Equihash proof-of-work solutions. The compatible Zcash/Wcash profile is Equihash (200,9).
Privacy · Shielded transfers
Shielded transactions provide privacy for transfers. That function is separate from the proof-of-work puzzle.
Merged mining · Pool layer
A compatible pool can reuse one Equihash work stream across both networks. Each chain checks its own target and pays its own rewards.
In this setup, Wcash remains a separate chain with its own state and rewards. Merged mining reuses participating pool work; it does not merge Zcash and Wcash into one ledger. Only pools that include the Wcash commitment contribute work to Wcash.