On XInput I can't press ZL and ZR at the same time. It used to work until the 1.9.0 update. It doesn't even work if I'm using the keyboard and mapping ZL and ZR to keys. However, it does work on DirectInput.
On DirectInput the R-stick seems to have some deadzone that I can't get rid of. I've set it to anything between 0% and 33% but it still feels like it's at 33%. If I set it to anything higher than 33% then the deadzone increases ingame too.

Steam Controller, 980ti, i5-4670k, 8GB RAM, W10 Windows Insider build 15063