Ctrl + Scroll to Zoom google maps (Is it bad UX?)

I'm not sure if this is bad UX. On the one hand, it allows users to scroll the page without the Google Map getting in the way (without it, you'll end up zooming the map). On the other hand, users might get confused with the change.

Now the million dollar question is, is there a better way to tackle this? Even better if there's a live example. OR is this the matter of priority?