removing polyurethane from hardwood floors

I am in the process of refinishing all the hardwood floors in my 1930's home. The old old finish was easy to remove with Zinsser Strip Fast Furniture Refinisher and we didn't restain and it looks beautiful. We put on several coats of a protectant finish that has a little bit of gloss to it. But the previous owner had refinished one room and it has a matte polyurethane finish on. This remover doesn't seem to budge this finish & I'm at a loss. I do not want to sand - the floors are in gorgeous condition & we love the warm look of our already refinished floors & don't want to deviate from that. This floor that I'm currently trying to strip butts up against the floors and stairs that I've already done so a uniform look is what I'm going for. Any tips as to what products will remove this finish will be greatly appreciated. Thank you!!!