Yep, can confirm it has an issue. htt ps://www.pianobook.co.uk/library/summer-piano/
In the meantime if you double click on the zip file, you extration tool should open and have a warning. Close the warning and then look for Tools. From there you may see ‘Repair archive’. Use that and a few seconds later it will create a new file with ‘rebuilt’ added to the beginning of the file name.
Then it should open, after which you can also delete and rename the files if you wish.