I reply your message but i'll post it here too.
here is the file I modify in default theme,
app/design/frontend/default/default/template/safitech/catalog/product/view/media.phtml
i change the size at line 64-66, my custom size is 522 and 237,
<div id="image">
<-------
-----------
-----------
class="jqzoom"><img <?php echo $style; ?> id="image<?php echo $i; ?>"
width="522px"
height="237px"
src="<?php echo $this->helper('catalog/image')->init($this->getProduct(), 'thumbnail2', $_image->getFile())->resize(522, 237); ?>"