The two instances of VOIPo primary line seems great for me now.
To avoid any routing conflict, I put the GrandStream on its own IP.

WideOpenWest allows 3 IPs from the Modem that you can pull with a switch or Hub.

I also found a WRONG hookup in my network that likely did not help in the past. I had an Ethernet cable that came from my router to the switch that ties to the modem! Plus the router was pulling its own IP from the switch, yet serving local IPs itself.

What threw me was the Grandstream kept pulling a local IP while I thought it was getting it from the modem ... It is now really with its own IP (no NAT).

With that cleared up I gave the ZyXEL another shot. Everything is looking good. The only "issue" I've seen/see with Zeus that worked on codeblue, was the VWMI/Stutter (and I put a ticket in).

My two line UNIDEN phone connects to the GS(Grandstream) and ZX(ZyXEL). The ZX is mapped so that port2 can dial using VOIPo, and I leave port1 as incoming, but not connected. (Two simultaneous CID calls to the UNIDEN gives it trouble knowing what to display!)

So VOIPo line1 IN/OUT, LINE2 OUT only.

OOH! A SUGGESTION:

I just realized that VOIPo needs something that gives a running total of regular minutes used in a time-period, or from your monthly cycle.

That would really be the outgoing CANADA/USA PSTN minutes. It is beneficial to see how many minutes are used monthly. It can let you put things in context for how heavy a user you are. If you are using two instances of an account, it can also show (for someone like me) that I am barely scratching the surface of phone usage.