If they provide lowball Zestimates, that allows them to buy homes for cheap. Or if they own the home, they can increase the value prior to sale.
Hard to trust when they could easily use this estimation system to their other business model's advantage.
Try to use a zestimate to negotiate the price on your next home. Watch how quick the experts laugh you out if the room.
The zestimate is just a nice quick way to get a ballpark value of a home. But I don't think they are playing any significant role in affecting market prices.
Others would insist that I match whatever numbers they found online - our standard response was to explain that Zillow won’t actually buy your house from you at the number they’re quoting, so we value their prices accordingly.