mcmansionhell's use is clearly fair use as it falls under both the criticism and parody exceptions. This might be why the Zillow SLAPP letter mainly focuses on supposed TOS violations. Whether unsigned web site TOS off on a page most visitors never see are enforceable at all is highly questionable.
But you can also make the argument that it's only fair use if you're using the photos to criticize and parody Zillow or the services they provide. She's not criticizing Zillow or its services but rather the subjects of the photographs.
Like you could stop someone using your image in a parody because you took the picture of your tie and they instead parodied your suit wearing. Doesn't work, the image stands by itself, the supposed purpose of the image is irrelevant to the copyright ... or am I wrong?
If I take a picture from Zillow's site and use it to teach a class about poor framing (ie photography technique) then the exception for educational use still stands.