I had one bad Zero nozzle jam with PETG. I mistakenly let the chamber drift up to 60 C and had heat creep, then made it worse by getting in a hurry. I’ve been 3D printing forever and definitely knew better. I eventually got it cleared and it’s been good ever since. I still print ABS-CF with a chamber temperature of 60 F but I’ll be much more careful with PETG.
I posted a BAD CLOG thread that may have some info that could help you. People posted very good and helpful info.
Good luck. Please let us know how your carbon fiber reinforced nylon printing goes.