When you use Safari browser on an Apple computer and download WPML and its add-on plugins’ .zip files, Safari will automatically unzip them. This happens due to Safari’s default behavior.
To solve this issue you can either disable this option in Safari or try using a different browser to download WPML and its add-on plugins.
To disable this option, open Safari->Preferences and in the General tab, uncheck the Open “safe” files after downloading option at the bottom.