The collection is composed of two parts: the main app, and the Asset Pack. The main app handles the code and logic and processing, and the asset pack stores the data. For a couple of different reasons (namely, the Asset Pack is very large and also not GPL licensed) we distribute the Asset Pack and the collection separately.
The good news is the collection can be updated with bugfixes and features without requiring a new Asset Pack! We use semantic versioning, so if you were on 1.0.0, an update to 1.0.X would be a bugfix, and an update to 1.X.X would mean bugfixes and new features. Only an update to a new major version like 3.0.X would require re-downloading a new asset pack/patch.
It's not corrupted, you're using a ZIP unarchiver in compatibility mode for the previous millennium. Use a modern zip extractor like 7-zip, or at least one that isn't choosing to actively sabotage you.