<?php
    global $post;
    $terms = wp_get_post_terms( $post->ID, 'product_cat' );
    foreach ( $terms as $term ) $categories[] = $term->slug;

    if ( in_array( 'z', $categories ) ) {

      Insert_extra_HTML/CSS/Shortcode_Here;

    } else {

      do_nothing_extra;
    }
    ?>