Open the ZA window (double click its Taskbar icon), navigate to "Programs" (left pane) -> Program tab -> select the program you want to "Unblock" & then Left Click on it to open a small "level of trust" window , select the desired "level of trust" or better select "? Ask" option.
refer the pic.
*img251.imageshack.us/img251/112/untitledzq5.th.jpg