A surprisingly frequent cause of an 'empty' or corrupted zip file is just that the download has not fully finished. 

In some cases your browser may show a file as having fully downloaded, even though it has not. If you try to download again and allow it to complete, that can help.

Another possible cause is the unzip utility you use. Macs in particular seem to have some issues with Windows zipped files. I use and recommend a free unzip utility for Windows called 7Zip and for Macs I quite like YemuZip.

If a download link is actually broken or not working, please let me know by submitting a new help desk ticket.