Nah, they're just extra data, that could easily go in the signature fields; it's definitely possible to add Zcash functionality to Bitcoin in a backwards compatible soft-fork.
Basically you'd have a pool of "shielded" txouts that could be spent with a zcash signature, without any requirement that a particular txout be spent for a given signature. Surpisingly easy upgrade all things considered; the main blocker is Zcash's crypto is very experimental and slow.
Basically you'd have a pool of "shielded" txouts that could be spent with a zcash signature, without any requirement that a particular txout be spent for a given signature. Surpisingly easy upgrade all things considered; the main blocker is Zcash's crypto is very experimental and slow.