I don't know why you want to balance your furnace load between the two zones, but anyway if you're comfortable, you can do it by raising the upstairs temperatur

I don't know why you want to balance your furnace load between the two zones, but anyway if you're comfortable, you can do it by raising the upstairs temperature. But to optimize for comfort, set both thermostats the same, and let the lower floor do more work. If you're heating the same amount of air to the same average temperature, I don't see why the overall efficiency would be different.