Hacking a ZyXel PK5001Z (4 port Modem/Router combo)

No.

However there are no modem/router combos that aren't dependent on non-free software sadly. At least not that I'm aware of. I did quite a bit of hunting a few years back too.

There may be a PCI-style card that is free software friendly. Good luck finding something that is compatible with todays DSL/Cable Modem standards though and will still work.

Most modems will worth with free software operating systems although don't themselves not depend on non-free software internally.

There is a reason I'm always wording things a bit oddly. There are a lot of devices or types of devices which have standards that make said devices compatible with free software operating systems although are themselves dependent on non-free software.

Just because you can connect to a schools access point for instance doesn't mean your not indirectly using a device dependent on non-free software. Much of the ISP infrastructure you depend on is not free software friendly.

One thing at a time.. one thing at a time..

If you don't want to be dependent on non-free software there is a long way to go yet!