Carlos Zambrano finally pitched worth his contract for the Cubs last night. He improved the Cubs' pennant hopes for the first time since July to beat the Pittsburgh Pirates 5-1 at PNC Park. ''That's all we need. We need 'Z' to pitch like he did today,'' said lead off hitter Alfonso Soriano, who muscled a two-run homer through tough hitting conditions into the first row in left field in the fifth inning. ''If we're going to [make the playoffs] we're going to have to have our No. 1 pitch like that. And he pitched like he's the No. 1 here.'' Pitching shutout ball into the seventh inning Saturday, Zambrano had been the biggest drag on the Cubs' playoff push over the past month, going 0-5 with a 9.42 ERA in his last five starts -- his slump culminating with a cascade of boos from the home fans Monday, followed by him blasting the fans.