Zaxia values a Mixed Use property by breaking it into its parts. If your property is part office and part retail, Zaxia shows you an office survey and a retail survey separately. Zaxia then adds the value of the office part to the value of the retail part to get the value of the whole property.
It helps for you to break the property down in advance.
You need to find the square foot area for each part. If your building has three stories with 1,000 square feet on each floor, you have a 3,000 square foot building. If the first floor is a store and the upper floors are apartments, the retail space is 1,000 square feet. Enter 1,000 square feet when Zaxia asks for the square foot area of the retail space. When Zaxia asks for the square foot area of the apartments, for that building, enter 2,000.
If you are entering financial information like the building's expenses, you want to handle that the same way. If the real estate tax bill is $6,000, you could allocate $2,000 to the retail space and $4,000 to the apartments. Or you might break it down another way. However you break it down, for the building in this example, the parts need to add up to $6,000.
Just think of your building as a building in two parts (or three or four, if it has a mix of three or four uses). And remember to keep the parts separate.