You have deployed a proof-of-concept application by manually placing instances in a single Compute Engine...

Create a single managed instance group, specify the desired region, and select Multiple zones for the location.

Create a managed instance group for each region, select Single zone for the location, and manually distribute instances across the zones in that region.

Create an unmanaged instance group in a single zone, and then create an HTTP load balancer for the instance group.

Create an unmanaged instance group for each zone, and manually distribute the instances across the desired zones.