There is something important missing from the ZCCA judging rules: the protocols for the judges themselves.
The ZCCA document only includes things like the process to certify a person as a judge, the classification of cars, and recordkeeping. It has nothing to say about how the judges should conduct themselves while judging.
If you look at a document like a judging manual for something like a concours d'elegance, it will outline the protocols that the judges themselves must follow while judging the cars.
Just like the spectators at a car show, who are not to touch the cars, so should the judges of a car show. Judges should not touch the cars, at least not without permission, to open the door or the hood or trunk, and they shouldn't be getting in and sitting on the seat to try the steering wheel or brakes or lights, switches, glovebox, etc. The same goes for someone looking at an engine. They key word is look, not touch, or grab wires or a hose, etc. Those things can be done by the car's owner and the judge can watch. Even if something must be touched, it can be done with a clean cloth or wearing a clean glove.
That's just the basics. Things can be developed further.