<p>Anyone know difference between those two? 
For now only difference I see is that regional require >= 3 zones.</p>

<p>Found good explanation <a href="https://www.terraform.io/docs/providers/google/r/container_cluster.html#additional_zones" rel="noreferrer">here</a></p>

<blockquote>
  <p>A "multi-zonal" cluster is a zonal cluster with at least one
  additional zone defined; in a multi-zonal cluster, the cluster master
  is only present in a single zone while nodes are present in each of
  the primary zone and the node locations. In contrast, in a regional
  cluster, cluster master nodes are present in multiple zones in the
  region. For that reason, regional clusters should be preferred.</p>
</blockquote>
