Ok,
I'm running Win10 and cannot replicate by the ZIP method or by the manual method. I don't know why it is broken bar that the ZIP file for you is corrupt but not for me. Therefore either:
- Something to do with your download of the ZIP, so you could get from here: https://github.com/gjb2048/moodle-theme_essential/releases/tag/V3.4.0.1
- Or that the WAMP you are using is configured incorrectly. So try using the Bitnami one and see if it happens: https://bitnami.com/stack/moodle.
- Or something else.
G