I have my "Zoom / Printed Size" set with "1" as its hotkey. This will zoom the drawing to 100%. From there I'll move the cursor out of the drawing area and use the +/- numeric keys to zoom in/out. As Dean shows, the "Zoom Factor" can make difference on the amount of zoom for each plus/minus movement.
Designer, Deluxe, Expert, Basic, Platinum
RedSDK enabled, except in 2018
Windows 10, 64-bit