@TylerDurden So where are you entering the PPPoE username and password for your connection, I have a vague memory that the set-up is done via some cloud app, i could be wrong but if this is the case you need an internet connection for it to work which you haven't got because you can't set it up. There is a work around, by using another router to connect to the internet, or even by reconfiguring the zyxel as a router to allow the Nest to be setup in when it is in access point mode then reconfigure the zyxel to a bridge modem. There have been many discussions about this on the net and a lot of people just give in and don't use the Google nest as a router or just get rid of it.
I said the Google Nest set up was a nightmare in an earlier post when you couldn't get the HG612 working on G.Fast.