Drupal 6 syntax for theme_imagecache

gistfile1.php

<?php
// The raw path to the image.
$path =  $node->field_product_image[0]['filepath'];
// Let imagecache generate a different sized image using 'Product_large'
$large_path = imagecache_create_url('Product_large', $path);
// Render the original image and save the path to the large one in the tag.
// Your output will be something like: 
// <img src="blah.jpg" large_img="large-blah.jpg" class='img-swap' />
theme('imagecache', $path, '', '', array('large_img' => $large_path, 'class' => 'img-swap'));

?>

Drupal.behaviors.swapProductImages = function(context) {
  // Find all the images that have a swap on hover. 
  $('img.img-swap', context).mouseup(function(){
    // For each image, swap in the larger sized image we saved in the <img /> tag.
    zxcImageViewerII.SwapImage('tst6', this.src, $(this).attr('img-swap')); 
   }); 
}