In a nutshell: The addition of a new "Zoom" binding separate from "Zoom In" and "Zoom Out" that's intended to have a single axis control assigned to it (such as the X or Y axis of a gamepad stick, a gamepad trigger, or the scroll wheel of a mouse). This would also bring it in line with the available zoom bindings for map view, which has "Map Zoom" and "Map zoom for controller" (personally, I've set the latter to Modifier (Left Shoulder Button) + Right Stick Y-axis).
