The gamble of shooting megabudget Matrixes back-to-back might have seemed bolder if The Lord of the Rings hadn't done the same -- and far more lucratively. As The Matrix Revolutions (R, 129 mins., 2003, Warner) hits the small screen, let's explore some other big-screen multitaskers. The Three Musketeers (1974) and The Four Musketeers (1975): Producers Alexander and Ilya Salkind chopped their sprawling, nearly four-hour epic in two, but wanted to pay their cast for a single project. The resulting brouhaha led to a ''Salkind clause'' that became part of the SAG contractual boilerplate. Back to the Future Part II (1989) and III (1990): Part II's see-ya-next-summer nonending was a virtual model for Reloaded's abrupt lead-in to Revolutions (funny, BTTF's grosses tailed off, too...). And in an interesting twist, Superman (1978) and Superman II (1980): The Salkinds, producing again, dumped director Richard Donner after the first movie -- though he'd simultaneously shot material for the sequel (partly to accommodate Marlon Brando's and Gene Hackman's schedules). Now theforbidden-zone.com is organizing a write-in campaign to release Donner's scrapped footage on DVD.