Google Maps (like PayPal checkout) is one of those sites that have so called frame-break-out scripts running to prevent them from being embedded. If you wish to embed a Google Map, you’ll need to get the iframe embed code (same way as you got the link, just choose embedding option) … inside that iframe code, there is a URL that you need to extract. Copy the complete code snippet to a text file and find that URL in the
src="..." part of the code.
Copy that URL and use that to create your FancyBox iframe link.