Z-Factor: The sum of cost changes incurred by local telephone companies which are beyond their control and which can, therefore, be included in the price cap indexing mechanism.

ZIP – Zero Interest Program: A program to provide loans, without interest, to residential customers to insulate or weatherize their homes.

ZORF – Zone of Rate Freedom: A procedure by which charter-party carriers (buses, limousines , shuttles, etc.) can increase their fares within a limited range above or below current prices without coming back to the Commission for authorization; this allows such companies to adjust pricing to changes in the economy.

ZUM – Zone Use Measurement: A method of pricing local calls and interexchange (toll) calls up to 16 miles in the San Francisco and Los Angeles areas; including discounts for late-night usage.