No, this isn’t possible. But you could connect a Sonos Port to one of the audio inputs on the CXA80 and stream music on the Arc and CXA80 at the same time.
And here’s an article on how you can use the NAS with Sonos:
https://support.sonos.com/en-us/article/use-a-nas-drive-with-sonos
Thank you for the prompt response! So with the Sonos port I could make the music sound simultaneously in both equipments right? Maybe with a risk of lack of sync?
Should be no loss of sync on Sonos part but you may need to tweak the settings on the CXA80 to minimize any internal delays.
Different manufacturers use different names, Pure Direct, Direct, something similar that removes the internal delay causing processing.