I have a mini-stick above my hat switch that acts as two analog axes. I have its Y axis (up/down) set up for zoom and I have its X axis (left/right) set up for map zoom by setting it like this:
MiniStick Y MIN = Zoom Out
MiniStick Y MID = Nothing
MiniStick Y MAX = Zoom In
MiniStick X MIN = Map Zoom Out
MiniStick X MID = Nothing
MiniStick X MAX = Map Zoom In
Basically the Minimum setting will "press a button" when its axis is in its lower 33% of range, the Middle or Center setting will "press a button" when its axis is in its center 33% of range and the Maximum setting will "press a button" when its axis is in its top 33% of range.