Water and electric heating with a single thermostat

I will have two types of heating in my bathroom: Water heated floor from air-water heat pump Electric heated floor with cable mat

I want to have a single thermostat operating in two modes:

• Water heating during winter
• Electric heating during other seasons when water heating is turned off

I found that Heatit Z-TRM6 thermostat supports both types of heating, but doesn't change the mode of operation - you either connect heating cables to the electric heating or water thermal actuator.

How can I achieve two modes of operation (with the help of Shelly relays and some setting in HA)?