After downloading the ZIP file, it's impossible to unzip it

After downloading the ZIP file, it’s impossible to unzip it. 

   unzip dw_page_1.0.5_quickstart.zip <br />Archive: dw_page_1.0.5_quickstart.zip <br />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. <br />unzip: cannot find zipfile directory in one of dw_page_1.0.5_quickstart.zip or dw_page_1.0.5_quickstart.zip.zip, and cannot find dw_page_1.0.5_quickstart.zip.ZIP, period. 

Can anybody help me?

Thanks