Eamonn,
Just a couple of points.The first would be to install MinimServer on the Zenith if you can. We have had other members with Innuos servers running to dCS Mosaic reporting odd behaviour otherwise. Early Zenith’s used to offer MinimServer pre-installed as an option but I do not know the current situation as Innuos have developed a long way since then with their InnuOS operating and control system. I am also not sure about compatibility of that with Mosaic. You may want to contact Innuos if you find problems interfacing with Mosaic to see if you can install MinimServer 2. Please read this link :
You can use Innuos Zenith as a USB streamer to Bartok using the InnuOS app. However USB is not the best way to go with dCS streaming products and the optimum sound is via a network connection which I think is what you want to do with Zenith as a server. Of course an alternative is Roon.
So, that lengthy internet cable that you need. There are all sorts of preferences expressed on this forum for such cables, I will stick to the dCS recommendation that properly accounts for the connectivity provided on their devices. Use an unshielded cable ( CAT 5e or 6 unshielded) and ensure that the cable is officially certified as meeting the standards for the CAT standard.