I have several WordPress themes in ZIP files on my hard drive. When I try to upload one, I successfully navigate to the directory and I see those files. But when I select one, it shows it to me where it would normally show the name of the directory; the filename doesn't appear in the box where it should appear and it says "No items match your search." So there seems to be no way to upload a theme.
See attached screenshot.
Could it be that your template .ZIP files are in a extract first package? Some developers and theme creators will package the template upload with auxiliary files like documentation. PSD and other file structures. For the customizr.3.4.21.zip it seems like that is a direct upload file but check just to make sure. If you can't get it sorted you should try to unzip the folder on your computer and manually install it via FTP. Hope that helps?
roy darling *my posts seem a lot shorter in my head