You may not be able to delete your rental listing. The problem is that although Trulia and Zillow are now one company, the websites they operate are different. Zillow allows for public participation but Trulia does not (you can't post for rent or for sale by owner on Trulia).
Now it gets interesting...Since the sites are linked, the information is shared - but there is no control of postings from the public in Trulia!
I hope for your sake the information will "age" and drop at some point.