aws elb enable-availability-zones-for-load-balancer --load-balancer-name my-loadbalancer --availability-zones us-west-2b
{ "AvailabilityZones": [ "us-west-2a", "us-west-2b" ] }
aws elb disable-availability-zones-for-load-balancer --load-balancer-name my-loadbalancer --availability-zones us-west-2a
{ "AvailabilityZones": [ "us-west-2b" ] }