I started using android auto with MRA in my car (xc40) a few days ago, because I wanted to see how it works before i used it on the carpuride.
I must agree on issues with the zoom option.
I think it is mainly caused by the difference in screen resolution and sizing if you compare phone and device.
But I do miss a zoom option on the android auto screen and an option to move around the map, with finger and pinching ,like Google maps can, to look a bit around on the map for example when stopped.