Controlling 2 devices from climate entity

Integrating my boiler system into HA. Got most everything working, i.e. boiler lockout over 60 degrees F, single device zones working properly. ESPhome based. Master bedroom has 2 zone valves that I’m trying to put onto 2 separate relays as follows:

 - platform: generic_thermostat
    name: Master bedroom
    heater: switch.relay_channel_1
    heater: switch.relay_channel_2
    target_sensor: sensor.lumi_lumi_weather_28344b04_temperature
    min_temp: 62
    max_temp: 75

Works, but only brings on switch.relay_channel_2, not both. If I remove the switch.relay_channel_2, it will bring on switch.relay_channel_1. Does generic thermostat only allow for one device to be controlled?

Cancel that, just read docs again. One device per instance.

I wonder if climate entities can be grouped?

Tried it. Didn’t work right for my situation.