zstd uses a fairly low compression level by default. If you run with `zstd -19 -o compiler.tlo.zstd stdlib/compiler.tlo` you will probably get much better compression than gzip, even at its highest setting.

That said, the tiny code footprint of gzip can be a real benefit. And you can usually count on gzip being available as a system library on whatever platform you're targeting, while that's often not the case for zstd (on iOS, for example).