Hello from Poland 
I wonder if it is possible to use simultaneous music playback in all zones - I mean that one song is sent to equal devices (amplifiers or DACs) at the same moment - without delay, with just one click - itâs like grouping a pair of zones into one - is this possible ? 
Yes. Make the zones in Roon.
Ah editâŚyou want to make zones of zonesâŚthat I donât know.
Hi Piotr,
At the moment Roon can only group like Zones. See this KB page for details. There are some pretty formidable technical obstacles associated with grouping different types of Zone, and grouping all types would be a technical miracle. I wouldnât plan on Roon being able to do that.
So there is some planning required if you want simultaneous whole of house playback. You will need to choose devices that support Zones of the same type. I would reccomend RAAT as the common type if you want to group Zones in Roon. Roon will always perform best with RAAT.
Just to clarify, this means buying hardware marketed as âRoon Readyâ, instead of âRoon Testedâ or anything else. You can see a list of the companies making Roon Ready products here: https://roonlabs.com/partners.html, and there is an unofficial list of Roon Ready hardware here: http://roonready.com/
Gentlemen, thank you very much - this is exactly the solution that I did not know yet: grouping zones (https://kb.roonlabs.com/FAQ:_How_do_I_link_zones_so_they_play_the_same_thing_simultaneously%3F)