Blake Coleman had a goal and an assist, Stefan Noesen had two assists, and Keith Kinkaid made 15 saves for the Devils (27-16-8), who won their third straight game and outshot the Penguins 38-16.
"Those guys work hard," Zajac said of Coleman and Noesen. "I'm just trying to keep up with their speed and tenacity. As a line, we're not going to score every night, but we need to generate chances and make sure we're tough to play against. If we can do that, we'll help the team."
WATCH: [All Penguins vs. Devils highlights]
Evgeni Malkin scored, and Casey DeSmith made 35 saves for the Penguins (29-22-3), who had a four-game winning streak end. They defeated the Washington Capitals 7-4 on Friday and are 5-5-2 in the second game of back-to-backs this season.
Penguins forward Sidney Crosby did not have a point for the first time in 12 games. He scored what would have been his 400th NHL goal 12:54 into the third period but it was waved off for goalie interference by Bryan Rust.
"I think we got outworked," Crosby said. "They seemed to be more desperate; that was definitely the case in the first two periods. We came out a little harder in the third, but we didn't win battles. You get a big win and you've got to be able to turn the page, and emotionally we weren't ready."
The line of Noesen, Zajac and Coleman combined for 12 shots, six hits, five takeaways and seven points. Zajac won 56 percent of his faceoffs (10 of 18).
"[Travis'] line was our motor, they got us going," Devils center Brian Boyle said. "We played well as a whole, but they made the difference when we needed it most. Scoring one goal in this league is hard, and he got two, so good for Travis because we appreciate everything he does for us."