Example on how to change the file name of the zip archive.

bulk-download-for-gravity-forms-change-zip-filename.php

<?php
/**
 * Plugin Name: Bulk Download for Gravity Forms - Change zip file name.
 * Description: Example on how to change the file name of the zip archive.
 * Author: VCAT Consulting GmbH
 * Author URI: https://www.vcat.de
 */

/**
 * Filter the file name of the zip archive (without extension).
 *
 * @param string $filename  The current zip archive file name.
 * @param array  $form      The GF form array.
 * @param array  $entry_ids The entry IDs of all files being added to the archive.
 *
 * @return string
 */
function my_bdfgf_download_filename( $filename, $form, $entry_ids ) {
	// We append the current date/time to the end of the file name.
	return $form['title'] . ' - ' . date_i18n( 'Y-m-d H:i:s' );
}

add_filter( 'bdfgf_download_filename', 'my_bdfgf_download_filename', 10, 3 );

/**
 * Filter the file name of the zip archive (without extension) just for the form with ID 2.
 *
 * @param string $filename  The current zip archive file name.
 * @param array  $form      The GF form array.
 * @param array  $entry_ids The entry IDs of all files being added to the archive.
 *
 * @return string
 */
function my_bdfgf_download_filename_form_id_2( $filename, $form, $entry_ids ) {
	// We append the current date/time to the end of the file name.
	return $form['id'] . ' - ' . $form['title'] . ' - ' . date_i18n( 'Y-m-d H:i:s' );
}

add_filter( 'bdfgf_download_filename_2', 'my_bdfgf_download_filename_form_id_2', 10, 3 );

The filter can now be used either for all forms or just for a form with a specific ID:

Applies to all forms:

add_filter( 'bdfgf_download_filename', 'my_bdfgf_download_filename', 10, 3 );

Applies to a specific form. In this case, form id 2:

add_filter( 'bdfgf_download_filename_2', 'my_bdfgf_download_filename_form_id_2', 10, 3 );