Base (OP Stack): The canonical Coinbase L2 bridge. To move ZARO to Base, you deposit it into the L1StandardBridge on Ethereum; the matching L2StandardBridge on Base mints an equivalent amount of the OptimismMintableERC20 representation. To move it back, you burn on Base and the bridge releases the locked supply on Ethereum. mint() is gated by an onlyBridge modifier — no human can call it.
BNB Chain & Solana (Wormhole): Wormhole locks the source token in a guardian-verified escrow and mints a wrapped representation on the destination chain. Burning the wrapped token releases the locked supply. The mint authority on the destination is the Wormhole protocol itself — a smart contract on BNB Chain, a Program-Derived Address on Solana — neither of which has a private key.
The math: at any point in time, the sum of all bridged ZARO across Base + BNB Chain + Solana equals exactly the amount locked in the corresponding escrows on Ethereum. The 1B cap is enforced at the Ethereum layer and is permanent.