Zanzibar Declaration: a statement adopted at a meeting in Zanzibar in July 2001 of trade ministers representing least developed countries in preparation for the Doha Ministerial Conference. It calls on WTO members to make a range of greater efforts to promote increased integration of least developed countries into the multilateral trading system. Among these are cancellation of debts, increased official development assistance and duty-free and quota-free access for products from these countries.

Zero binding: a legally binding undertaking in the WTO to eliminate customs duties altogether on defined products.

Zero-for-zero tariff reductions: a request/offer system for the achievement of tariff reductions in which the parties involved aim at reducing tariffs to zero (i.e. at eliminating tariffs) on a reciprocal basis in complete sectors, such as pharmaceuticals or wood products. The Information Technology Agreement is a recent example of this approach. See also requests and offers and sectoral trade negotiations.

Zeroing negative margins of dumping: when a group of closely related products is subject to a single anti-dumping investigation, some of the individual products may show a positive margin of dumping (i.e. they are deemed to have been dumped). Others may show a negative margin of dumping (i.e. they are deemed not to have been dumped). Once the pricing of the individual products in the group has been investigated, the relevant authority has to make an assessment for the group of products as a whole.