I might be misremembering but at runtime, the Node process loads .pnp.js, which is a kind of monolithic “compiled” modules file containing all the modules installed. No reading of the .zip files occurs at runtime. (Again, I might be misremembering or have misunderstood. Please confirm/deny this if you know.)

The pnp.js file has a list of modules, not the modules themselves. The modules are still read from zip files at runtime.

Yarn doesn't do any kind of compilation itself - that would be done by build tools like webpack.

I’d be curious how “read file from a zip that I know the exact path to” performs compared to “recursively walk the node_modules directory and dynamically lookup the location of the file”.