Re: ZR tremolo for RG?
Thats bizarre, seeing as every specification on the Edge Pro is superior to the Edge III. The saddles have the sound metal chip in them, the knife edges are harder, the fine tuners and general manufacturing are much better...etc.
I can only assume there is something wrong with your setup that you are overlooking. There is absolutely no technical reason whatsoever for an Edge Pro equipped guitar to be inferior to an Edge III.
Edit: Also, your description doesn't make sense. The Edge III and the Edge Pro BOTH allow the ball ends of the strings to be inserted. Are you sure you're not referring to some other bridge?