-EDIT-
Some additional thought on feasibility:
I mentioned how you need to assign three keys to, let's say, zeroing.
Key 1: Zeroing Adjust (let's call it that way)
Key 2: Zeroing Up (let's say you choose "mouse wheel up")
Key 3: Zeroing Down (say, "mouse wheel down")
That way, as explained, you hold the "zeroing adjust" key to use the "zeroing up" and "zeroing down" keys to zero.
However, if you simply leave the "zeroing adjust" blank, than the "zeroing up" and "zeroing down" keys will work on press, like right now in ArmA3. So you can keep them mapped to PageUp and PaigeDown and things will remain as they are now. You got the choice.
Important is, as explained, if you do use the "zeroing adjust" key, than it should work as an override key and make the "zeroing up" and "zeroing down" keys override any other function that are mapped to these keys (so you can use the wheel to zero and still use the wheel for other functions at other times, without conflicts).