Foreign merchandise (tangible personal property) imported from outside the United States and held in the activated area of a zone for the purpose of storage, sale, exhibition, repackaging, assembly, distribution, sorting, grading, cleaning, mixing, display, manufacturing, or processing, and tangible personal property produced in the United States and held in the activated area of a zone for exportation, either in its original form or as altered by any of the processes set out in this section, shall be exempt from state and local ad valorem taxation.