Amundsen & Columbus

With the two physical dial system of the Amundsen, I often use the right hand dial to easily zoom in and out on the map (ie, big picture versus detail), especially somewhere new.  I use it as a real map, old style - which being digital (and a GPS) is easy and quick to reference on the move - I never use it as a Sat Nav.

I've just noticed that the (better?) Columbus system has no physical dials....  How does one easily (and safely) use any zoom functionality on that?  One barely has to look away from the road when there is a dial to control the zoom?  I'm useless with touch screens at the best of times - is there some other knob or dial somewhere that conveniently doubles up for that purpose?  Or is it actually quite easy to use, as above but in a quite different way?

[ And apologies if it's already been covered - I tried the search here but I struggled to find anything. ]