What is the required pilot action with the loss of both primary and secondary zone controller channels?

When both primary and secondary zone controller channels are lost on an A320, the system defaults to a fixed temperature setting. This is designed to ensure continued operation and safety in the event of a significant failure in the environmental control system. The maintenance of a fixed temperature allows for basic environmental control to be sustained, which is critical for passenger comfort and safety during flight.

In this scenario, no specific pilot action is required, as the aircraft's systems automatically manage the temperature settings. This built-in redundancy and automated response help prevent an adverse scenario from occurring, thereby ensuring that the cabin remains at an acceptable temperature without requiring pilot intervention during a failure.

The other options do not apply in this situation because they would involve actions not needed when the system autonomously regulates the temperature after losing both control channels.