The only thing you can trust on that site is the sale amounts. Even that is nothing special to retreive. Sale amounts are public information that can be obtained from the assessor of all townships, cities, or villages in the United States.
As far as zestimates, those are a joke. They assume straight-line appreciation nationwide based on the cost of goods annual increase which is an ENORMOUS fallacy. Every market is different and just because COG went up, does NOT mean housing appreciated in the same manner.