Andrew Cheng focused on improving the correctness and maintainability of zero-knowledge proof verification across multiple repositories, including risc0/risc0-ethereum and hyperledger/besu. He addressed compatibility issues by aligning Groth16 verifier input handling with the snarkjs library, ensuring that only the expected public signals are validated and preventing potential memory errors. In Java and Solidity, Andrew refactored error handling in hyperledger/besu by replacing magic numbers with predefined constants, reducing risk and improving code consistency. His work emphasized robust input validation and standardized error management, contributing to more reliable smart contract and API development within the zero-knowledge proof ecosystem.