Hi Andy, it's quite possible there's nothing wrong with your workbook. A twbx is a zipped package containing your workbook and data, so try unzipping it yourself, and then open the workbook using the .twb file.
If that works, you may have found a problem with Tableau Desktop that's worth reporting to tech support.
A zipbomb is a file in a zip archive that, when unzipped, expands to a size much larger than would be expected (the error message indicates that the expanded size is greater than 101 times the compressed size). The idea is to protect against someone intentionally distributing a small file that expands to something ridiculously large. Note the error message says "Possible zipbomb" since high compression ratios are possible.