Manipulate the files uploaded via Gravity Forms before they are stored

Looks like I was using this class to do this: http://gravitywiz.com/rename-uploaded-files-for-gravity-form/ and added the filter in myself after line 207, ie.

    // replace merge tags
    $form  = GFAPI::get_form( $entry['form_id'] );
    $value = GFCommon::replace_variables( $value, $form, $entry, false, true, false, 'text' );

    // MOD: add a filter here to hook into filename change
    $value = apply_filters('gravity_forms_upload_filename', $value, $entry);

$value will then contain the full path to then uploaded file which can be hooked into and zipped so you can return the zip path instead.

Here is the snippet I was using to load GW_Rename_Uploaded_Files:

add_action('init', 'my_forms_rename_uploads', 11);
if (!function_exists('my_forms_rename_uploads')) {
 function my_forms_rename_uploads() {
    if (!class_exists('GW_Rename_Uploaded_Files')) {return;}
    $form_ids = array(
        1, // list of form IDs to load renaming class for
    );

    // --- get all file upload fields ---
    foreach ($form_ids as $form_id) {
        $upload_field_ids = array();
        $form = GFFormsModel::get_form_meta($form_id);
        if (isset($form['fields'])) {
            // --- get upload field IDs ---
            foreach ($form['fields'] as $field) {
                if ($field->type == 'fileupload') {$upload_field_ids[] = $field->id;}
            }
            // --- set class arguments ---
            $args = array(
                'form_id' => $form_id,
                'field_id' => $upload_field_ids,
                'template' => '{filename}'
            );
            // --- initialize rename uploaded files class for fields ---
            new GW_Rename_Uploaded_Files($args);
        }
    }
 }
}

Hope that helps...