Another vote..

We are also running ZCM on 2008 R2 Datacenter Edition on VMWare. One
Datacenter license per ESXi host allows unlimited VMs. Of course you
can install lower editions, but running actual datacenter VMs is a
pretty common best practice. It helps with tracking licensing using MS
tools.

You can upgrade lower editions upwards
(standard->enterprise->datacenter) with the DISM command, but as far as
I can tell from googling there isn't a way to downgrade.

So I hope and pray 11.3.1 is different.

Regards,
Phillip E. Thomas