Tutorial files can't be unzipped

I'm trying to follow along here: Lay out and design your app or website |

It went into an infinite loop of .zip to .cpgz in Chrome and Yandex browsers. Tried terminal and got this message:

End-of-central-directory signature not found.  Either this file is not

  a zipfile, or it constitutes one disk of a multi-part archive.  In the

  latter case the central directory and zipfile comment will be found on

  the last disk(s) of this archive.