Is ethernet output a possibility for the Innuos Zen MK3

Just an update...Here's the response I received from Innuos:

Ethernet and USB are very different outputs, it's not just a matter of changing cables. If you want to connect via Ethernet, this means the ZEN works only as a server and sends the file for the Gustard to play. This is done via a protocol called UPnP. You can turn the Zen into a UPnP server by going to Sense App > System > Settings > UPnP. Choose the Native UPnP option. However, this way you won't be able to use Sense for playback, you will need an app such as BubbleUPnP on Android or mConnect on iPhone/iPad to browse and play your music - or if the Gustard has a app then use the recommended app from Gustard.

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You should check to see what inputs are best for your DAC as there is usually one or maybe two that are optimized for performance. I think your DAC also has an i2S input, so that might be worth checking into as well. I’d think Gustard could give you that info if you don’t have it already. Best of luck.

It's well reported that ethernet is the best input for the R26.  My mistake was thinking the second ethernet port must be an output.

Could I put a connect a switch to the Zen MK3 and output from that switch to the DAC as a work around?

I think ethernet out from a streamer/server to a DAC is a very unusual architecture, but it is what Sonnet uses for the I2S protocol. It's a LOT more common to do this via HDMI, but Sonnet doesn't provide an HDMI port. I guess they have their own way of doing things. This is how I have my Sonnet Morpheus DAC connected to the Sonnet Hermes streamer. The ethernet connection on the Morpheus uses the same port as the USB input, but you have to physically uninstall the USB card and insert an ethernet I2S one in its place. 

I think @carlsbad2 is right in that the two Ethernet ports basically form a mini switch. In that case, try connecting the Gustard to the 'Streamer' port with a network cable and then follow the instructions on connecting network streamers (link) and then enabling Sense UPnP (link).