I was wondering where i could download the default u-boot firware pre-flashed in
the CC-MX-JN58-Z1 module.
You can find pre-compiled images including u-boot here:
This is not necessarily a shipping version. If you need an exact shipping version please open a support case by emailing firstname.lastname@example.org and provide a P/N of the module and revision, it looks like 5XXXXXXXX-XX Y.