@blackheart it's all approximations with units though isn't it? I can judge that that group of T1 units is going to beat that other group of units without needing to know the exact composition of each group, and I can't believe that the top players are able to make specific counts of specific units on both sides before engaging. Even if you've got the mental capacity to do that it would be energy better spent elsewhere.
I was wrong about zooming in, I don't really go more than 50% at any time unless I'm positioning some fiddly buildings.
What I do do is use lasso select all the time and select the specific units I want from the bar at the bottom. This is partly why I find Supreme Economy so essential because finding and clicking individual mexes is not easy for me.
The three levels on SupEco don't quite make sense. It's meant to show unringed, ringed and upgrading for each tech level and I'm not convinced it works 100%. But double click the unupgraded icon, choose which of those mexes is in the safest place to upgrade, and get back to what you were doing. So much easier than have to devote time to finding the damn things and clicking in just the right place.