Zendesk Webform hook_alter
hook_form_alter is a drupal API function. You can google "hook_form_alter" and the 1st result will be the API documentation for this function; it includes examples.

Using this "hook" function you can inject, or otherwise change, any form in your drupal website. A "form" is an HTML construct that can send data to a webserver via either POST or GET.

So, you can create a custom drupal Module (which consist of in this case an .info file and a .module file). In your  module you can create a function that implements "hook_form_alter" and adds in the zendesk field.

A simple simple example of this would be:

# in the below examples lets assume you have named your module folder as "zext" (kinda short for zendesk extensions .... i dunno :P

# in zext.info
name = Custom Zendesk Form Extensions
descrption = We want to add custom fields to the zendesk form.
package = Other
core = 7.x

# in zext.module
&lt;?php

/**
 * Implements hook_form_alter().
 *
 * Alter the zendesk form and add a custom color text field.
 */
function zext_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == 'zendesk_form') {
    $form['zendesk_favorite_color'] = array(
      '#type' =&gt; 'textfield',
      '#title' =&gt; t('Favorite Color'),
      '#description' =&gt; t('Please tell us what your favorite color is!'),
      '#weight' =&gt; 99,
    );
  }
}

# that is all the code that would be in the 2 files.


With the above 2 small pieces of code we have modified the default zendesk_form (I assume its $form_id is zendesk_form ... it may be different examine the module's code to see how it IDs the forms ...) and added 1 single new custom field to allow the visitor to submit their favorite color. Drupal doesn't store these values anywhere -- they are just passed onto Zendesk upon form submission; You simply need to create the folder + 2 files and install the module in the drupal administration. Your module folder should be called zext.

There is alot of documentation online for creating modules, and using hook_form_alter. Look on drupal.org and Google.

Happy Coding!