An HDMI output will send video and audio to another zone in the house, presumably offering all the benefits that come with the main output.
Forget about multizone audio, Denon and Marantz receivers are getting something new – something even cooler. The newest receivers from both companies give you a second HDMI output, which offers the ability to run multizone video.
Both receivers offer 4K upscaling as well as the kinds of audio features you'd expect from Denon and Marantz. With zone audio, you have to give a few things up, since the outputs are usually just stereo, but we're guessing that the upscaling, seven channel output and audio features carry over to the second channel.
You'll be able to find this feature in the Denon In-Command line as well as the Marantz SR series.
Source: Electronic House