It would nice to receive answer to this non-answered question.
From my current research's seams Horizon doesn't have any integration with Cloud Director.
Also, it seams advised to deploy dedicated vCenter, ESXi just for Horizon Services. This is obviously huge waste of resources for current Cloud Providers based on VMware.
There is also an old blog post from 2013. about this https://myvirtualcloud.net/how-to-horizon-view-and-vcloud-director-multi-tenant-daas/ but since this is from ten years ago stating there is no integration between Cloud Director and Horizon.
However, VMware might did some progress in this matter in last 10 years.
Let's hope that someone can shed more light on this matter.
