How do you get to build new RZs?

So, I'm level 30 and I never really understood how you get more RZs.
This morning I bulldozed an omega RZ. It was just a construction site, never upgraded. I was expecting to get back an extra "RZ point" as you would with factories and shops, but that didn't happen.
EDIT: I was mistaken; I didn't bulldoze an omega RZ. The game doesn't let you do that. It was already upgraded once.
Best Answer
You're only allowed to have up to 3 new construction-site RZs, so in order to get more "RZ points" you have to upgrade one of them that's already been placed. And you can't bulldoze them.
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