I had the same issue. If you’re on a Mac or Linux (not sure the equivalent on Windows sorry) you can repair the archive using this command in Terminal.
zip -FF 381243_TheSummerPiano_ChristianHenson.zip --out SummerPiano.zip
This will create a new archive called ‘SummerPiano.zip’ which you should now be able to extract. Let me know if you have any trouble, especially if you’re not familiar with command-line tools.