You need to extract the theme from the zip file.
The zip file you received as a part of your purchase is not the theme.
The theme is contained within: XStore_ Multipurpose_Woocommerce_Wordpress_Theme\XStore Theme
Look for the zip file that looks like: “XStore_Theme_vX.X.X.zip”. Extract this to your desktop. This is the actual theme file you need to install.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.