Using z_taxonomy_image_url() in a normal WordPress loop?

I’m looking at using the standard WordPress loop for your function.

Is this possible? Because its not working for me right now…

Normal Loop :

<?php while ( have_posts() ) : the_post(); ?>
    if (function_exists('z_taxonomy_image_url')) echo z_taxonomy_image_url();
<?php endwhile;  ?>

Also, what about a custom query?

Custom Query :

<?php $query = new WP_Query(array( 'category_name' => 'category-one', 'posts_per_page' => 9, 'paged' => get_query_var('paged'))); ?>
<?php while( $query->have_posts() ): $query->the_post(); ?>
     <div <?php post_class('category-post-content'); ?>>
     <img class="category-thumbnail" src="<?php if (function_exists('z_taxonomy_image_url')) echo z_taxonomy_image_url(); ?>" />
     <h2><a href="<?php the_permalink(); ?>" rel="bookmark" title="Permalink to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
</div>
<?php endwhile; ?>

Right now I’m using this, and it’s not working.

Help!

http://wordpress.org/extend/plugins/categories-images/