The services you create can be active in one, two, or all of your zones. This setting can be managed in the admin center.
Admin Center -> Services → Select a service → Action → Configuration tab → Configuration → Zones
If you want to choose the zones in which you want this service to be available (active), you have to unmark the “all” checkmark and add the zone(s) you want separately, as shown in the image below:
Then click on “Submit” to save the applied changes.