Zeus basically is basically a simple way to work with GraphQL without having to constantly look at the schema. It takes your schema (even a really gigantic one) and creates TypeScript types for it. What does that give you? The ability to know what is in the schema right from vs code (since everything is typed) and having the certainty that you can work with it in a type-safe way without messing anything up. With that you can work on your frontend stuff without asking a backend dev for anything or even looking at the schema!
Read the rest of the docs for a walkthrough of the installation process, a breakdown of the features and the introduction of a new neat thing called Thunder ⚡ which gives you direct control of a GraphQL query as an async function with a typed result!