Fancybox Help

Hi,

How can I get the thumbnails to appear in Fancybox?

I am using this snippet to display the ‘normal’ Featured Image:

<?php $image_url = wp_get_attachment_url( get_post_thumbnail_id($post->ID) ); ?>
		<a class="fancybox" href="<?php echo $image_url; ?>" alt="<?php the_title(); ?>">
			<?php the_post_thumbnail( 'projects-larger-thumbnail'); ?>
		</a>

And this is the code I have for the Secondary Thumbnail:

<?php if (class_exists('MultiPostThumbnails')
    && MultiPostThumbnails::has_post_thumbnail('projects', 'secondary-image')) :
        MultiPostThumbnails::the_post_thumbnail('projects', 'secondary-image', NULL, 'projects-secondary-image-thumbnail'); endif; ?>

Thanks in advance