Change the project post type name to something else (for example NewName).

Project slug

The url of Divi projects contains /project/ like https://www.mydomain.nl/project/projectname/

To change the project slug, add the following code to the functions.php file of a child theme:

// START change 'project' slug (url prefix)
function et_projects_custom_slug( $slug ) {
    $slug = array( 'slug' => 'NewNames' );
    return $slug;
}
add_filter( 'et_project_posttype_rewrite_args', 'et_projects_custom_slug', 10, 2 );
// END change 'project' slug (url prefix)

Code language: PHP (php)

Project category slug

The url of Divi projects contains /project_category/

To change the project slug, add the following code to the functions.php file of a child theme:

// START change 'project category' slug (url prefix)
add_filter( 'register_taxonomy_args', function($args, $taxonomy, $array_object_type) {
  if ($taxonomy == 'project_category') {
    $args['rewrite']['slug']='NewName_Category';
  }
  return $args;
}, 10, 3);
// END change 'project category' slug (url prefix)
Code language: PHP (php)

Complete rename projects (incl. text)

Add this to your functions.php of the child theme, and change the slugs AND the categories and tags. Then re-save permalinks twice.

// START change 'project'
function rename_diviproject_cpt() {

/* Rename the custom post type */
    register_post_type( 'project',
        array(
            'labels' => array(
              'name' => __( 'Voertuig', 'divi' ),
              'singular_name' => __( 'NewName', 'divi' ),

        ),
        'has_archive' => true,
        'hierarchical' => true,
        'public' => true,
        'rewrite' => array( 'slug' => 'NewNames', 'with_front' => false ),
        'supports' => array(),
        'menu_icon' => 'dashicons-marker',
    ));

/* Rename the category */
    register_taxonomy( 'project_category', array( 'project' ), array(
        'labels' => array( 'name' => _x( 'NewNames Categories', 'NewNames Categories', 'Divi' ), ),
        'hierarchical' => true,
        'show_ui' => true,
        'show_admin_column' => true,
        'query_var' => true,
		'rewrite' => array(slug' => 'NewNames_Category')
    ) );

/*Rename labels/tags */
    register_taxonomy( 'project_tag', array( 'project' ), array(
        'labels' => array('name' => _x( 'NewNames tags', 'NewNames tags', 'Divi' ),),
        'hierarchical' => true,
        'show_ui' => true,
        'show_admin_column' => true,
        'query_var' => true,
		'rewrite' => array(slug' => 'NewNames tag')
    ) );

}
add_action( 'init', 'rename_diviproject_cpt' );
// END change 'project' 
Code language: PHP (php)