That's odd. I use the same controller but I haven't tried to change the binding for zooming. (I think default is dpad down while using the right thumbstick to zoom). I use betterUI for gamepad improvements but ever since the last big update it's not been working well. IDK if that's related or not but there have definitely been some changes since global achievements that have made using a gamepad harder than it used to be. I hate whatever they did that messed with the inventory view -- so much so I've played far less.