Zillow will always be inaccurate in a great deal of cases. One major problem is that the zetimates are based upon what is in the assessors records which in many cases is wrong. For example, my primary residence is listed in the tax assessors records 200 sq ft smaller with 1 less garage and 1 less bedroom than I have. It does not account for my location, view upgrades or yard.
Airline tickets are commodities, essentially all are equal but for the price and (window, middle aisle). Homes are all unique and have many attributes that could never be accounted for by a algorithim.