This is how I have mine setup - see attached.

Zoom V3 is nice because you get you regular phone and your VOIP line on the same phone, just press # to switch.
I have EsatBT 3MB connection and never have problems with call quality.

Downsides
- It works well, although the zoom V3 seems to loose it's registration sometimes when there is an IP address change, I should - perhaps once every two weeks.
- It would be nice if the zoom could support multiple SIP accounts - I guess I couls always stick an IP phone onto it.

Can you share how you configured network on Zoom V3 ? I have gotten mine to work once, but now it seems I can't configure WAN anymore. I have IP, Sub-net and Gateway provided to me by ISP + ethernet wire, but DSL Static option or any other won't work.

Do I have to change NAT settings?