Marantz CDR611 and audio multiroom

Hello I am new to Homey world and I’m trying to read the most I can.
One of my goal is to improve my house audio multiroom experience.
Now I have a Marantz CDR 611 connected to a manual speaker selector from Pyle with 6 zones and volume control (I repeat everything manual).
My 6 zones are Bathroom, Kitchen, Bedroom, Garden 1, Garden 2, Studio. In each zone I have two normal speaker (someone better someone older and worse)
Now I am going to do this, buy 2 sonos amp for kitchen and bathroom that have the best speaker, buy sonos one for bedroom and studio and use my marantz for the garden speaker.
Then I would like to create group of speakers in Google Home and use them from Spotify.
My problem is with integration between Marantz 611 and Google Home because Marantz has only airplay and bluetooth even if is a network receiver. But I have a Chromecast audio in analogic input of Marantz so I can stream to it.
So my idea was to use homey to pilot the marantz and I downloaded the marantz app and I can switch on, switch off and fix the volume but unfortunately I can’t change the input.
Probably my model is not so smart to speak with marantz homey app.
My idea right now is to clone the remote of marantz with infrared and use it to select the input.

I have written everything in details because if someone has other suggestions to me to improve my multiroom audio system I am open to receive. Most of all because it seems to me that the sonos amp has a very high cost without so high technical specs. Do you know if there is something different I can do? Maybe a sort of smart speaker collector which is programable from homey.

Regards and thanks