Namada is a decentralized application (DApp) platform that is built on top of the Ethereum blockchain. It is designed to make it easy for developers to create and deploy DApps, and provides a set of tools and services to help them do so.

Zcash, on the other hand, is a cryptocurrency that was designed to provide a high level of privacy and anonymity for its users. It uses zero-knowledge proofs, a form of cryptography that allows users to prove the authenticity of a statement without revealing any information about the statement itself, to enable transactions to be made without revealing the sender, recipient, or amount involved.

So, the main difference between Namada and Zcash is that Namada is a platform for building DApps, while Zcash is a cryptocurrency that focuses on privacy and anonymity.