Reported by 'Dimentio' to me, yesterday, after getting him on 2.50.2:

He required DXGL to run not only in fullscreen, but to run ZC, period. ZLaunch-w did not help, nor did any mucking about with his ag.cfg file. I have the final ag.cfg file that he is now using, but apparently something in Win 8.1 did not like running ZC. He encountered an error 'Video mode unsupported' using my ag.cfg file (I run XP and Win 7).

The strangest error that he reported was that the ZC window started flickering, or phasing, ceasing to exist, and reopening, as ZC tried to load.

I don't own anything with Win '8.anything'. I have no motivation, desire, or even reason to run that pile of rubbish OS, to try to check any of these problems; nor do I know his HW config, video config, or driver selection. Thus, I've no way to confirm, or check any of these problems. AFAIK, Gleeok and Saffith both still use XP too, so this could be a tricky one.