help-wordpress

This is what I have, I want to add images to it for parent categories only.

<ul>
<?php wp_list_categories(depth=1); ?>
</ul>

This is what I've tried with no resolve.
<ul>

<?php foreach (wp_list_categories('depth=1') as $cat) : ?>
 <img src="<?php echo z_taxonomy_image_url($cat->term_id); ?>" /><br/>
 <div class="product-price">
<a href="<?php echo get_category_link($cat->term_id); ?>"><?php echo $cat->cat_name; ?></a>
 </div>
 <?php endforeach; ?>

</ul>