When you seek the services of an agent and pay them money to help you buy or sell real estate they represent to you that they are qualified to assess the value of the real estate being bought and sold and are somewhat morally obligated to you by virtue of the money you paid them to provide you with accurate information.
Professional licensing requirements are supposed to ensure they are sort of kind of qualified.
Someone you didn't hire which is providing a ballpark guess on the value of your property to help people do preliminary research before they buy has minimal enough obligation to buyers and none at all to you.
We can see that the obligations of the agents above attach both to the fact that they are brokering 6-7 figure transactions and to the fact that you contracted them. Its hard to imagine what you believe the obligation is supposed to attach to in zillows case.
Its not even clear that regulating zillow according to each individual states laws would accomplish save placing unconstitutional limits on free speech. Plantiff doesn't even want that they want a club to compel zillow's silence or desirable speech. Surely cloaking it in bs doesn't make this any less unconstitutional.
The problem in Zillow's case may simply be the legal system... And that will vary greatly from state/county to state/county. The real estate market is very protective of itself.
Real estate brokers and appraisers also sell information (not real estate).