The ZBox is what she played with Sunset on the game stream. The flashback shows younger Fluttershy playing on an NES.
The thing is, why would it be an NES? Fluttershy and the others are supposed to be, like, 17 or something. If this is supposed to be Fluttershy when she was in elementary school, wouldn’t that only make it around 2010? Why is she playing on a console from the 1980s?