You cannot delete your account.
Contact them via http://www.support.zippyshare.com/index.php?act=tickets&code=open
Fill out the form and ask for removal of your account. Include your account information, like username, password and email address.
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.