The internet connections are usually for listening to "their" default radio stations via URL like BBC, etc.
You can change them via editing URL to what you like, but as a multiple audio card? Then squeeze would have to have a URL or maybe IP address?.
Maybe some manufactures would allow an ip address instead of a URL.
You could only get up to 3 zones depending upon the receiver (2 channel stereo only) but if you want multi-zone go with a distributor.
Feed it your stereo source and distribute it.
Or, am I totally misunderstanding you?
(I did just off working 3 12 hours nights in a row).