The real estate websites are aggregators, they pull data from all over the place, lots of it wrong, and it would be a full-time job just to watch over them. However, I have phoned aggregator sites and successfully obtained edits that benefited my clients. Brokerages buy ads on these websites, and therefore they tend to listen to agents.
Lic. Real Estate Salesperson
Charles Rutenberg LLC
Lillian Tramantano, GRI, CHMS
Successfully Marketing & Selling Real Estate For Over 26 Years!
Aside from that, the important thing is that buyers who are looking in Sands Point are most likely going to be using a realtor, and will have some level of trust in that person. With any luck, they will be using a loan officer who is familiar with the area, and will be helping even at this stage to guide them as well. I am not an appraiser, but I have looked at enough appraisals to know what is important, and what they will usually adjust for. I also cross reference properties on the Nassau County assessor's site so that I know the square footage of the various homes, and also important in Sands Point, the property size.
From you question, it seems that you might be a seller, and not a buyer. You may not be able to do anything about zillow, but I would be happy to talk to you either way.
Century 21 American Homes