I wonder how well the map re-routing works if it's a route created in Garmin Connect. I tend to use that anyway for navigable routes as the maps are as good and it's an easier BlueTooth download to the device.

On an Edge 1000, you need to swipe to the map screen, then press the screen, then the + or - button, On the Wahoo you have to toggle to the map screen then use the 2 buttons on the side of the unit to zoom. With any unit it's always a few button pushes.

In general, I find that if there's information I need to see on the map, I'll stop the bike and pay attention to the map, kind of like using a smartphone in the car, it's easy to get distracted by the device.