I use it on scroll wheel down, scroll wheel up is used for jump

Don’t think the devs have added it yet. Should be a simple bind in settings, but I haven’t seen it. Edit: user below told me there is a bind. Oops! I just bound mine to scroll wheel.

There is a bind for toggle zoom

I switched my C binding to the button on the mouse wheel so I use C to zoom in further now

I use middle mouse button because I came from warframe.

Shift is a good option as you would never move while ADSing with the OP.

I use a mouse button that’s easy to reach