Seems odd to me that Zwift mandate the maximum graphics setting we can use. If we’re happy with any potential frame rate drop, we should be able to select the highest graphical setting.
Anyway, judging by Jon Mayfield’s reply here:
https://forums.zwift.com/t/ultra-graphics-settings/9582/2
A GTX960 would use ultra, let alone a 1060. So that being the case, you get my vote.