well, you've not mentioned triggers so i expect there is where you'll need to do the most work.
I'd suggest you use 3 zoom settings, getting a -zoom xxx amount is actually fairly annoying. just use -zoom high/low/"blank"
Will use 3 different triggers, but i doubt this will be a problem.
Is it just a normal map (like twisted meadows) or are you doing other things? for i would be ensure of how to change the amount of workers if you kept it the same, personally i would use the unit palette to just dump some workers on the map.