How to Created Multiple Instances on Luci OpenWRT Router

I have two distant physical locations each with two different ISP’s and each with a OpenWRT router running Zerotier successfully, including Lan to Lan bridging of the subnets at each.

I now wish to add two instances of Zerotier on each router to route through each ISP for redundancy. Not sure how to do this. I tried adding a 2nd instance in the config file and it does create a 2nd zerotier device which initially get the same MAC address. Then I changed the MAC address on the 2nd interface and it now show two interfaces, but only one joins the network. There’s probably also the issue of those interfaces using different underlying ethernet devices with different default gateways.

Can anyone give me the steps to setting up multiple instances on OpenWRT Luci?