public static function shipping_zone_add_method() {
		if ( ! isset( $_POST['wc_shipping_zones_nonce'], $_POST['zone_id'], $_POST['method_id'] ) ) {
			wp_send_json_error( 'missing_fields' );
			wp_die();
		}

		if ( ! wp_verify_nonce( wp_unslash( $_POST['wc_shipping_zones_nonce'] ), 'wc_shipping_zones_nonce' ) ) { // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
			wp_send_json_error( 'bad_nonce' );
			wp_die();
		}

		// Check User Caps.
		if ( ! current_user_can( 'manage_woocommerce' ) ) {
			wp_send_json_error( 'missing_capabilities' );
			wp_die();
		}

		$zone_id     = wc_clean( wp_unslash( $_POST['zone_id'] ) );
		$zone        = new WC_Shipping_Zone( $zone_id );
		$instance_id = $zone->add_shipping_method( wc_clean( wp_unslash( $_POST['method_id'] ) ) );

		wp_send_json_success(
			array(
				'instance_id' => $instance_id,
				'zone_id'     => $zone->get_id(),
				'zone_name'   => $zone->get_zone_name(),
				'methods'     => $zone->get_shipping_methods( false, 'json' ),
			)
		);
	}