How the heck is a portable 637KB .exe that doesn't require any installation, extraction or admin rights to run, "too heavy weight"?

This one might interest you, although it's quite old.

https://unxutils.sourceforge.net/

Busybox's shell is ash, but the above set includes an old zsh IIRC.

Note also that the Frippery Windows busybox is available as a 64-bit version, in case 2gb is not enough (easy with some big awk associative arrays).