upon speaking to H! B, I'm not able to have their router in bridge mode and also have line rental from them (home phone, etc) despite the fact I have another VoIP router.
Regardless is there any way to have all go through the Synology router, leaving the ISP one downline and only for parsing of the traffic g internet/home phone?
and how would I do this
Well, it is more likely to be 'unsupported' than 'impossible' assuming H!B use standard VOIP protocols - but for a variety of reasons, including hardware lock in, I prefer not to have phone service from the ISP.
Assuming that the H!B router has the VOIP adaptor on its LAN Bridge, my first thought would be to connect the LAN bridge of the H!B router to the LAN of your router, having disabled DHCP on the H!B router and having given it an address for the admin interface on your LAN which does not conflict with the DHCP pool on your router.