Zach improved code quality and maintainability across the OffchainLabs/go-ethereum and ethereum/go-ethereum repositories by focusing on documentation accuracy, test hygiene, and configuration clarity. He refactored comments to align with actual function names, reducing comment-code drift and supporting easier onboarding. In Go, he removed unused constants, duplicate tests, and redundant log noise, streamlining gas calculation logic and enhancing test reliability. Zach also updated test expectations and corrected configuration output, ensuring that error messages and display values matched intended behaviors. His work addressed subtle bugs and maintenance overhead, demonstrating a methodical approach to code refactoring, debugging, and configuration management in Ethereum client development.