maybe your question is not very clear....do you want to watch a movie with 5.1 audio in the living room AND music via HEOS in other rooms?.... or do you want to add HEOS speakers to your 5.1 and possibly make a 7.1 system?...
but maybe this page will help you...(https://support-de.denon.com/app...)

Since it has Heos built in, yes. why shouldn't it be able to?
i don't use it myself. but for this reason, i very much assume that it does.

unfortunately I can't say, I'm not technically savvy enough😏