<?php foreach (get_the_terms(get_the_ID(), 'productcategory') as $cat) : ?>
    <?php if($cat->parent < 1): // Only Parent Category, if you want the Sub-category, delete the If?>
        <img src="<?php echo z_taxonomy_image_url($cat->term_id); // URL of the Image ?>" alt="<?php echo $cat->cat_name ; // Name of the Category ?>" />
    <?php endif; ?>
<?php endforeach;?>