NO - you certainly don't want to be playing around with the buttons too much - find a zoom level of your choice and stick with it. The 520 Plus can go into the zoom mode with the 2 left side buttons but it's not meant for dynamic zooming during a ride. It's more for you to choose your zoom level, press enter and the zoom level setting is saved for the map. You can't use anything while the Zoom mode is active so you have to decide on a zoom level and close it and continue as normal.

Yes - it would be nice to have a dynamic zoom button (like your 705)...but it is what it is. I can live with it once i've settled down on a zoom level setting, i'll know what i'm getting and what to expect from the map. It's probably do-able for me because my requirements are quite simple. Might be more challenging when one uses a power meter, heart rate and cadence etc.....

I currently have a main screen and a second screen with additional info. I populated it with all my required fields....Distance to Go, Time to Destination, etc. so that i minimise screen changes. Ideally I want to live off just 1 data screen and the map screen (for navigation purposes). If i choose my fields well i can come close.

The price to pay for a truly bright brilliant color screen is that it's not touchscreen. That's perfectly fine with me as once you've settled on your required information for a ride you really have no reason to muck around with the screens. Again - make a decision and choose the zoom level of your choice and don't change it during the ride. Currently I am using zoom of 200m.....it could change in the next few rides. Once you're familiar with the zoom details you should not need to be constantly zooming in/out. Zooming in / out might be OK on a touchscreen but the buttons are not suited for such dynamic functions.

And....another benefit of buttons (unlike a touchscreen) is that the screen can be pristine and not smeared with sunscreen and oily fingers.