so I downloaded this zip file of an mp4 movie (3.9GB) as a reward for a kickstarter a while ago but every time i tried to unzip it 'failed crc checks' so tried z-zip ( version 9.2 ) (which the ...

If you ask anyone which software they use to archive or extract files on Windows, chances are that they either use WinRAR or 7-Zip. After all, these are the two most popular tools for this purpose.