You are using MAC computer probably with Safari browser that unzip the file by default.
Do the following so your zip files don’t open automatically after you download them:
1) Go into Safari Preferences.
2) Page titled General.
3) Scroll down to the bottom.
4) Deselect the box with the text “Open safe files after downloading”.
5) The plug-ins will now download as a .zip file which uploads
seamlessly to WordPress.
use another broswer/PC
use FTP method