If I understand your problem properly - unfortunately no.
The properties (and hence the expressions in them) are applicable to each zone separately.
Your zones can not 'talk' to each other and therefore one zone does not know the area of any other zone.
Yes the schedule can give you all the zone values, but the calculations are not done in the schedule, they are performed in each zone before they get to the schedule.
It is possible, but not automatic, if you add a property that is associated to the zones and manually enter the main zone area in this property.
Then you can create another property with an expression that calculates the ratio for you.
This can then be listed in your schedule.
Barry.
One of the forum moderators.
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