Hello
You would have 2 Essentials kits, one version 6 and one version 7 so you would have a vcenter server and 3 hosts (2CPU) for each kit.
In the image you sent from vcenter Essentials 7 I see the following licenses entered:
vcenter Essentials 7
VMware vSphere Essentials 6
vSphere Essentials 7
Since the vcenter is Essentials, I am not sure that it can manage 2 different types of tenders (Essentials).
.
Is there any reason why I need to have this mixed license burning?.
I will keep looking, but your case is out of the ordinary