Thank you for letting me know. I've now put a link on my page with a smaller file (219 MB instead of 570MB).
The issue was that I put Unreal's standard assets into my project as well (and didn't end up using them), but that apparently contributes 351MB to the zip file.
And I also noticed that level 2 linked to level 5 instead of level 3, which is fixed in this version as well.
So thank you :D