Locche by clear UD. Tszyu had an excellent sense of timing coupled with the intelligent, stalking pressure he applied, but I think Locche would work in the pocket and not let Tszyu time him with full leverage on the right hand especially. Tszyu is one of my modern favourites and was usually more troubled by fast, aggressive fighters who could push him back, as opposed to defensive specialists. This, however, is Locche we're talking about. If Cervantes and Ortiz struggled with Locche, so would Tszyu. It wouldn't be a complete shutout though.
Locche would frustrate and decision Tszyu, whom I like alot as a fighter over 15 rounds for a clear decision win.