I have a fresh install of WordPress and I am unable to activate themes that I have installed from zip files.

When trying to activate the theme the page takes minutes loading and then the entire WP site crashes (admin panel too). I have tried different themes.

Themes that are installed directly from the WordPress theme store on the admin panel work fine.

I have tried increasing the memory on php.ini file but still it doesn't solve the issue.

I also tried changing WordPress versions(upgrade and downgrade) , deactivated plugins, but the result is the same.

I am using: Ubuntu 16.04 PHP 7