Compilation Overview
zksolc is the compiler used by ZKsync to convert solidity code to zkEVM-compatible bytecode. It uses the same input format as solc but the output bytecodes and their respective hashes. Internally it uses a custom-compiled solc
Dual Compilation
To allow switching back and forth between EVM and zkEVM as defined in the Execution Overview, we compile the same contract with solc and zksolc. This dual-compiled contract can then be freely translated between both environments as needed. As such every contract in Foundry ZKsync always has two bytecodes attached - EVM bytecode and zkEVM bytecode, which are not equivalent.