Sample code
PHP Code:
zen_image(DIR_WS_IMAGES . $pd->fields['products_image'], $pd->fields['products_name'] ,195, 160, 'longdesc="'.zen_href_link(FILENAME_PRODUCT_INFO, 'products_id='.$pd->fields['products_id']).'"'); 
While it is expected that the param I passed in should be in the new image, it was actually overwritten in this function and hence never appears (unless a certain condition is met, which I believe is the case that neither width nor height value is passed)

Not exactly a Zen Cart bug, but kinda annoying and inconvenient.