What is the importance of zoning?
The larger an area to be cooled or heated, the larger the surface area between the conditioned space and the environment so, the more heat will flow and the more energy will be used to maintain comfort.
Some ducted air conditioning systems have the capacity to be zoned to function between "day-night". This means, the air conditioning will only be able to be used in the living areas during the day and in the bedrooms at night.
By incorporating a zoning feature the required size of the air conditioner is reduced and its use is reduced, since it either cools/heats one area or the other, and not both at once.
Zoning a building may also reduce the air leakage rate, saving more energy, as walls form barriers to internal air flow.