Active Zones can be accessed by clicking control+E and scroll down in the list till you find it.
It will give an overview of the , well active zone's on the map, such as start positions, etc....
Evidently on an empty map there is nothing to be seen.
Also the 'Add' button is useless here and does not work, as all zone's are to be setup via Mission Zone's in the toolbox.
The only use for this i found so far, is that it gives you :
-an overview of the zone's on the map,
-you can also edit the zone's here, and
-additionally, you can 'add' extra information to it if necessary, eg the zone has a double function, for example both a 'tower zone' and a 'strategic important AI zone'....or any combination. I have not tested all of these.