VLAN's from different VDOMs into same Security interface zone

having separate vdoms means the interfaces in different vdoms cannot share a common zone, a vdom is basically a 'virtual' firewall instance each with its own routing table, interfaces/vlans, etc. 

maybe you would want a redundant interface instead https://community.fortinet.com/t5/FortiGate/Technical-Tip-Creating-a-redundant-link/ta-p/196577 ?

Or, I think it's simply not possible. VDOMs are equivalent to physical separated FW units. One vdom can't refer or share another vdom's properties.

Toshi

how about creating a LAG interface in the root vdom, adding both both ports physical ports to the LAG interface, then assigning the LAG interface to the VLAN interface to each VDOM?

config system interface
edit "LAG-CORE"
set vdom "root"
set type aggregate
set member "x5" "x6"
set lacp-mode active
next
end

then add "LAG-CORE to each VLAN Interface rather than the physical port? Won't this mean I have redundancy i.e:

if x5 goes down traffic will still pass both both vdoms because each VLAN interface is assign to LAG-CORE?

I think my initial post was very explanatory!