The general approach to scaling with privacy tech is to 1) optionally hide transaction data 2) execute the transactions within the private execution environment 3) provide a proof that this execution was done correctly to the main chain, that is exponentially cheaper to verify than execution of the transaction data. It doesn’t really matter what privacy tech is used.
Unfortunately, while this scheme has incredible properties (see: roll_up for one instantiation), it should never be used. A bug, such as one that allows the operator to mint themselves a bunch of coins, in the invariably extremely-complex off-chain circuit/code/whatever is used as privacy tech is impossible to prove on-chain. Blockchain are about auditability, not verifiability. In addition, proofs for these systems are usually extremely expensive to generate, and are monopolistic rather than competitive like mining, tending towards becoming permissioned.