Is it possible to allow zip files to be uploaded in WordPress?

Here is a action that works on my site:

add_filter('upload_mimes', 'custom_upload_mimes');
function custom_upload_mimes ( $existing_mimes=array() ) {
    // add your extension to the mimes array as below
    $existing_mimes['zip'] = 'application/zip';
    $existing_mimes['gz'] = 'application/x-gzip';
    return $existing_mimes;
}