add_filter('etheme_get_terms_args', 'sort_filter_brand_z_to_a', 10, 2);
function sort_filter_brand_z_to_a($args, $taxonomy) {
    if ($taxonomy === 'pa_brand') {
        $args['orderby'] = 'name';
        $args['order'] = 'DESC'; // Z → A
    }
    return $args;
}
