Thinking about this more, is there any reason why, at least until the DDK is extended, that we couldn't do the following:
Use the DDK to create a device for each HTD zone. I'm not SURE this part will work, but if we are lucky and the HTD feedback matches some currently supported feedback type when you change the volume, then...
So now you have six "devices" like "HTDz1", "HTDz2", etc. Then create a room for each zone, and in each room an activity for each input connected to the HTD. There shouldn't be anything stopping you from then just going in and out of rooms with Roomie and controlling each zone independently.
The question then becomes is it possible to have one screen that shows the status of all the zones in one place? I don't know, but I've got an idea this plan breaks down back at the beginning, unfortunately. I've successfully created a custom IP device using the DDK (just power to a projector), and I read the instructions about a billion times and stared and stared at all the examples, and I'm still not sure I understand exactly how feedback is supposed to work. But I can tell it's somewhat limited to some standard volume responses, and if the HTD doesn't conform, well, it all breaks down right there.
--Donnie