In ArmA3 you have the option to toggle ZOOM + and ZOOM - (press zoom + once to zoom in and a second time to zoom out), or Zoom + / - hold keys, but there is no way to zoom in and out continuously.
Like when I put the zoom to the scroll wheel, I want to scroll the wheel up to only zoom in (and when I keep scrolling up when max zoom is reached, it does nothing), or down to only zoom out.