Honestly, it looks like you ran speaker wire into the volume pots... ideally you would have run a back haul infrared relay remote control to a line level preamp driving an amp that drives one speaker per channel.
A possibility is to forget the in wired and go wireless. Get some active wireless speakers and connect them to your source.
Now, let me ask you.. what is your source like? Do you have your music in a network? Do you want in walls or are you OK with speakers mounted on a shelf or a stand? If the latter, you could set it up so that you have something like this:
A cheap Android Tablet.
Run something like VLC media player.
Something like a NuForce DAC-2 that connects to your tablet via a power OTG USB cable.
Run USB power into the cable.
Take the output of the DAC to either active speakers or get a Parasound Z-Amp and drive your speakers.
If running an NAS with an MP server you can connect directly via VLC over WiFi. The latest VLC player supports MP players directly, it will find them when you search the network.
If running a simple network with a WiFi access point you can connect the tablet to the computer holding your media files over WiFi and play the music files directly via VLC. You can use ES File Explorer for this.
I do this in two of my rooms at home since my digital audio files are in an NAS. I also have three other systems that are connected via Ethernet ( my main HT works that way).
Admittedly this is a bit complicated but it gives you total flexibility. I take one of my tablets outdoors and use headphones.
I did hard wire my HT's side and rear speakers in ceiling speaker but again, that's a one amp channel to one speaker cable. No volume control at speaker level. A 7.1 controller runs the system, all in one room.
Eons ago, before our complete house rebuild, I put built in ADS L300s in my living room walls with a back haul remote control ( infrared pickup with its own wire to an infrared transmitter) that controlled a dedicated receiver in the den. That worked great. I think this is what you would have wanted to do, huh?
Honestly, I think you miss wired the system for multi zone stereo. You are going to have to rethink how you want to take music around the house.
If you want to keep your inwalls, you need to control the volume before the amp not after. And assign one amplifier channel per speaker. That might mean ripping into the walls, again.
OTOH, if you don't care about keeping the in walls, you can go with active wireless speakers, but you will still have to drive a wire between them and a power cable to the main speaker in each zone.
Sorry.
