For us agents, I would not want to comment on specific property in the public place either. The homeowner's privacy is invaded. If this were my own house, I'd feel my house is unfairly scrutinized.
Zillow's estimates can be deceiving sometimes so you would have to have a Realtor pull the comparables from the neighborhood. Zillow bases their estimates on other similar homes that sell in the area but they never go inside a home. So if you have been going to open houses or have been looking at homes with a Realtor, you know how different two colonials can be once you get inside.