Barry Zito delivered on one of the biggest stages yet during six up-and-down years in San Francisco. Zito pitched the NL West-leading Giants past the Los Angeles Dodgers 4-0 on Sunday night to extend their division lead to 5 1/2 games, coming through in among the most important outings of his tenure on this side of the bay. “This game’s obviously bigger because not only is it against our rival in the West, it’s the Dodgers, too,” Zito said. “Being 5 1/2 up, we like where we’re at. We certainly can’t rest on our laurels. We have to fight every day, and that’s something we’ve been doing all year.”