General Aviation flight instructor reported holding at VOR a NORDO aircraft flew through holding traffic resulted in evasive action and an NMAC.

Narrative

At TFD VOR at XA:46Z; Aircraft Y was in the stack at 3800 ft. about to cross the TFD VOR for the ILS 5 CGZ in VFR conditions for a practice approach. The stack at TFD is well known within the practice area south of the PHX class bravo airspace; as well as being noted on the sectional charts. The hold was as published on the ILS 5 CGZ (R-228; 1 min legs; right turns) and there were people above and below (nothing unusual there). An aircraft came from the East (around the Eloy area (AZ88) and flew through the stack at 3800 ft. while not on comms with anyone within the stack. Evasive action was necessary; for otherwise a midair collision was certainly probable. The aircraft that violated this stack was Aircraft Z; flying west bound at the 3800 ft. altitude. Aircraft Y had a course that would allow it pass in front of the violating aircraft and avoid a collision.Aircraft just traversing through this area with no regard to frequencies or concern with the amount of traffic in combination with the IFR training that occurs with student pilots and low time instructors may lead to a midair collision one day.