So, it's been quite some time. The apartment is done so no more construction work. But I ended up changing the whole setup. My initial setup with pi zeros dind't go so well. It worked 90% of the time but sometimes the relays would bounce although I had them debounced (well I guess not that good) and with the whole cabeling I built an antenna, that started switching whenever some one walked through the room, so back to the basics, added opto couplers an rc's so the antenna behavior was gone, but everytime I pluged something in or out of the 230V Sockets some light would turn on or off. As my wife started to question the whole project I didn't bother to check if the power regulator of the pi was a mess or whatever the problem was. This is yet to be investigated. I bought the eq3 RX/TX boards. connected them to the relay board and the light switches and it works. It's great that I have a working solution but it's sad that it isn't my solution. I add some pics so you see what my Idea looked like.
