From DiskInternals Research:
The zip file format is the most popular form of data storage. It is widely used for backup and transfer of information over the internet. As any format with a well-defined structure, it is highly sensitive to corruptions. In case of even a minor corruption of the file structure standard zip tools will no be able to extract its content. This is because all zip tools check archives for integrity. If CRC values of the original files of an archive don't match the extracted ones, the standard tools won't extract them. In such a case DiskInternals ZIP Repair helps repair zip structure and extract the contents of the archive. Full automation of the recovery and a wizard-like interface make zip repair no more than a snap.