Hi, I'm not a bot..
Sounds like a passionated project, is not too easy to maintain that large database in MS-Word, Harry the first step is to ensure that the data has the same format so we can easily import them in a bulk mode, or do you mind to load each property manually to the new site?
I'm very well versed in web applications, I make them using Python-Django and a native set of tools, HTML, JS, CSS, Bootstrap, based on that we can create the site you have in mind, and yes, using the Google Maps API, what is not totally clear to me is the Zillow part, are you a realtor? Do you want to manage the properties on your site and replicate the status on Zillow? Although I have not had the oportunity to work with Zillow, it's API will allow me to integrate your site with them.
Finally, I can do this for you, but I'm afraid I'm pretty out of the budget. If you are flexible with that then let me know.
Also, take a look into my profile and navigate through my reviews it will confirm you that I take my business seriously.
I'm a Software Engineer and I want to help you.
Would like to get some feedback.
Thanks
Martin O.
~