Your global footer is most likely within a PHP file, which is not necessarily accessible within Wordpress.
- Locate where your PHP files are hosted - you may want to reference the following: https://wordpress.org/support/topic/where-do-i-find-my-php-web-files
- It's pretty common for PHP files to be accessible from the your web hosting service (HostGator, Rackspace, GoDaddy, etc.). Need to know where your site is hosted? This is a great tool to help you: http://www.whoishostingthis.com
- It's also very likely that your Google Analytics code is installed in the global footer. If you know where your Google Analytics code is installed, then you should install the Zift analytics embed code in the same file.