In Google Cloud parlance, "regional" usually means "transparently master-master replicated across the availability zones within a region", while "zonal" means "not replicated, it just is where it is."
Slight nit: "zonal" doesn't necessarily mean "not replicated", it means that the replicas could all be within the same zone. That means they can share more points of failure. (I don't know if there's an official definition of zonal.)