With 1:16 left in overtime, the Penguins had a 3-on-0, but Rask broke up Evgeni Malkin's pass across the crease intended for Kris Letang.
Zucker made it 2-1 at 9:47 of the third period.
"It's always nice to score but, you know, for me, I think it was a lot more than just getting chances the past games," Zucker said. "I don't think I was playing the right way. I don't think I was playing a good game. I wasn't really skating and playing the way I can, so I was happy just to be out there and skating, trying to make some plays, holding on to pucks, and obviously the goal is always great, so I'm happy for that. But we didn't get the win, so that's really the ultimate disappointment there."
Malkin sent Kasperi Kapanen on a breakaway to tie it 2-2 at 16:44. It was Kapanen's first goal with Pittsburgh after being acquired in a trade with the Toronto Maple Leafs on Aug. 25.
The Penguins have trailed in every game during their five-game point streak.
"I think we've been trailing a lot of games now, and it's always a good quality for a team to kind of come back and at least get that one point," Kapanen said. "I think for us we've just got to be ready right off the hop, so it wasn't our best in the beginning, but after that I feel like we started getting better as a team."
Marchand gave the Bruins a 1-0 lead with a shorthanded goal at 7:41 of the first period. Nick Ritchie scored a 5-on-3 goal at 7:58 of the second period to put Boston ahead 2-0.
NOTES: Pittsburgh played without defenseman Brian Dumoulin (lower body) after the second period. … Penguins defenseman Cody Ceci played his 500th NHL game. … Pittsburgh forward Drew O'Connor had an assist playing 10:51 in his NHL debut. … Ritchie played his 300th NHL game. … Bruins defenseman Matt Grzelcyk (lower body) participated in the warmup but missed his second straight game. … Bruins forward Jake DeBrusk (lower body) did not play after the first period. … Pittsburgh's last win at Boston was 3-2 in overtime on Nov. 24, 2014. … The Penguins were 0-for-6 on the power play, the Bruins were 1-for-3.