Joe, I've stripped a localized area in the left hand window recess/reveal of our Burro
trailer just forward of the window. Stripping was for the purpose of cosmetic repair to the surface. I used 12% ammonia; I was cautious about not allowing the solvent to run down the side of the trailer and had no markoff below the area removed.
I sprayed the bondo repair with a rattlecan primer and paint
using soft masking (cardbd. mask raised above the surface except at the window frame). Matching color cast is a pain so after the paint
cured for a week, I recoated the area with RMP which masks discrepancies of color and also surface texture. (Yes, Virginia, there is a slight amber or bronzy tint to RMP which can be put to use.)
If indeed ZEP and Red Max are the same material from the same manufacturer, then the proprietary stripper for ZEP should work to remove either one of these coatings assuming that the RMP is discontinued and no longer available.