the 32 bit version is restricted to about 3 GB of RAM, so not going to make a difference. the reason i mentioned it is that 64 bits is explicitly labeled as beta softwar, for testing only. 32 bits is considered 'stable' and the proper version of 4R7. you probably have to drop down a subdivision level or two from your…
upper limit i've ever reached in zbrush was about 75+ mio polygons per subtool as i recall. my general impression of the 64 bit version isn't all that positive though. i had random crashes even just switching subtools or subdivision levels. perhaps try to rebuild your mesh in the 32 bit version? i went back to Z4R6 because…