We have no expertise on Lightspeed. (In fact, we are not experts on any server, but of course since we test on Apache we do have some working knowledge of it.) Lightspeed .htaccess is not compatible with Apache, so you will need to be sure that the rules you have work for Zenphoto. With the 1.4.5 release that is significantly simplified. All the rules need to do is redirect any URL that does not point to an actual file to the Zenphoto root index.php script.
Perhaps some user has working knowledge of Lightspeed and can help you. But please note that when you self-host you do need to learn how to use the software you select.