I couldn't find anything in the source or javascript that would indicate it's google... it looks like they are using SWF/Flash which I am pretty sure Google would not be using.

I posted in their blog --
Tasty Info Behind That Swirly Text - Zillow Blog - Real Estate News and Analysis

Hopefully they will supply an answer.

Eric



-------------------------------------------
Just to follow up, they did reply... this is old now, perhaps we should get them to provide an update

"Hi Eric: Diane from Zillow here. For our mapping technology, we use third parties to provide us with data and rendering tools, but pretty much everything in our Flash mapping tool was custom written by Zillow. Thanks for visiting our blog and your interest in Zillow."

__________________