A VFR pilot in a holding stack awaiting their turn to conduct a practice approach to a non-towered airport reported an NMAC when another aircraft flew through the holding pattern not communicating with other aircraft.

Narrative

At TFD VOR at XA:22Z; Aircraft Y was in the stack at 4500 ft. holding in VFR conditions awaiting a lower altitude to shoot 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 4500 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 4500 ft. altitude. 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. A separate report will be filed for a 2nd NMAC that also occurred within this area.There is plenty of area around to traverse if choosing to go West bound without going straight through a highly intense IFR training area; and neglecting to go a safer route may one day lead to a fatal collision.