"Nobody likes to lose. We're tired of it," Zimmerman said.
Redding allowed just a single by Pedro Feliz in the second inning and walked three batters in seven innings. He outpitched Cole Hamels, who gave up one run and five hits in eight innings.
Redding retired 14 straight batters after Feliz grounded a single to center. He walked Ryan Howard in the seventh and left after walking Geoff Jenkins to start the bottom of the eighth.
Luis Ayala came in and retired the next three batters. Jon Rauch pitched a perfect ninth for his first save in two tries. Rauch got the win in the opener, after blowing a save while filling in for ailing closer Chad Cordero.
The Nationals are 3-0 for the first time since 2003, when they were the Montreal Expos. No team based in Washington has started 3-0 since the American League's Nationals opened 4-0 in 1951.
The Nationals haven't had a winning season since they moved to Washington in 2005. They finished in fourth place last season after being last three straight years, including the final season in Montreal.
"We believe," Redding said. "We believe we can compete and play with anybody in the league, whether it's Philadelphia, New York, Atlanta or Florida."
The defending NL East champion Phillies fell to 0-2. Poor starts are nothing new in Philadelphia. The Phillies opened 1-6 three times in the last four years and were 4-11 after 15 games last season.
Zimmerman gave the Nationals the only run they'd need with his second homer in the sixth. He hit a 1-2 pitch the opposite way into the right-field stands leading off the inning.
Zimmerman also made an outstanding defensive play at third base to prevent trouble in the seventh. He started an inning-ending double play with a diving stop on a hard shot by Pat Burrell.
It was Zimmerman who hit a solo homer with two outs in the bottom of the ninth to give Washington a 3-2 victory over Atlanta in the debut of $611 million Nationals Park on Sunday night.
"That's why he's the face of the franchise," Nationals manager Manny Acta said. "He's going to have a long career."
A 30-year-old right-hander pitching for his fourth team in the majors, Redding shut down a potent lineup that's led the league in runs the last two seasons.
Redding improved to 2-1 with a 2.19 ERA in seven starts against the Phillies. He was just 3-6 in 15 starts in his first season with the Nationals last year, but should've had a better record because his ERA was only 3.64.
"He was tremendous, a great outing in bad conditions," Acta said.
A stiff wind that blew straight in and cold temperatures made it difficult for pitchers and batters at hitter-friendly Citizens Bank Park.
Hamels, an All-Star in his first full season in the majors last year, was sharp. But the left-hander made one mistake more than Redding.
"I was trying to go away. It was out of the strike zone," Hamels said.
Notes: Nationals GM Jim Bowden said there's no timetable on a return for LF Elijah Dukes, who was put on the DL after straining his right hamstring in the season opener. ... INF Felipe Lopez, who has never played in the outfield in the majors, soon could be playing left field. "He's a great athlete and he has a great attitude," Acta said. ... The Phillies had been 6-0 when Hamels pitched at least six innings against Washington. Hamels is 4-2 with a 2.49 ERA in 10 starts against the Nats. ... The last time an opponent one-hit the Phillies was Chicago on July 2, 2003. Cubs starter Matt Clement pitched seven innings in that game.
