That type of water heater looks like a fairly standard Tanks style water heater used in the US. I don’t think there is much you can do to control it with ST. However for your situation I think that is OK. Leave the water heaters alone with their internal temperature control. What you need to do is control the circulation pumps with your thermostats. When a pump come on and water temp in the tank drops the flame will come on automatically. I’ve seen small homes heated this way in Northern Wisconsin USA.
I’m not sure I would use a qubino relay just because you would have to locate the relay near where you want to know the temperature (in the room). You should be able to us a plain 220v relay for each pump, a 24volt transformer (or whatever voltage they use in Egypt for heating control systems), and zwave wall thermostats. locate the relays and transformer by the pumps and run small thermostat wire to each thermostat to power it and send signal to the relays controlling the pumps.
