product-image.php

Orginal:
<a class="woocommerce-main-image zoom" itemprop="image" href="<?php echo wp_get_attachment_url( get_post_thumbnail_id() ); ?>" rel="prettyPhoto[product-gallery]" title="<?php echo get_the_title( get_post_thumbnail_id() ); ?>"><?php echo get_the_post_thumbnail( $post->ID, apply_filters( 'single_product_large_thumbnail_size', 'shop_single' ) ) ?></a>

Replace with:
<a class="woocommerce-main-image zoom" itemprop="image" href="<?php echo wp_get_attachment_url( get_post_thumbnail_id() ); ?>" rel="prettyPhoto[product-gallery]" title="<?php echo get_the_title( get_post_thumbnail_id() ); ?>"><?php echo get_the_post_thumbnail( $post->ID ) ?></a>