WordNet sense 1 (a quantity of no importance):

aught, cipher, naught, nil, nix, nothing, null, zilch, cypher, nada, zero, goose egg, zippo

WordNet sense 2 (a code of letters and digits added to a postal address to aid in the sorting of mail):

postcode, ZIP code, postal code

WordNet sense 3 (forceful exertion):

energy, vigor, vigour

WordNet sense 4 (a fastener for locking together two toothed edges by means of a sliding tab):

zipper, slide fastener

WordNet sense 5 (move very fast):

hurry, speed, travel rapidly

WordNet sense 6 (close with a zipper):

zip up