Stojković opened the scoring in the 22nd minute, volleying home after Sunderland failed to deal with a corner. The midfielder then turned provider, clipping a pass into the path of Beljo, who finished neatly in the 39th minute to give Dinamo a commanding lead.
Sunderland improved after the break and struck the woodwork three times, while Wilson Isidor had a goal ruled out for offside following a VAR review. But the Black Cats could not find a way back into the contest.
Le Bris acknowledged the contrast between the two halves and praised his players for their response.
"We had two different halves," he said.
"The first one was difficult, but I appreciated the reaction in the second half. It was much better, with more quality and experience on the pitch.
"We created many chances, but it wasn't enough. We are still combative and the players tried until the end to show something different."
The Sunderland manager knows the result leaves his side needing to respond quickly, but insisted the difficult period could help define the group.
"This situation will define us. When it's tough, we stick together and we'll be combative until the end," he said.
"I'm so convinced that this team will bounce back. We recover quickly and we go again, with belief and the quality we have in this squad. We have to work hard to change this moment."
Dinamo coach Jerko Leko was delighted with the performance, particularly the intensity his team showed in the first half.
"The first half was very good. The energy was what I was speaking about in the past two days," he told UEFA.
"We know how to play football, but we need to be aggressive in defence. We also need to be aggressive with wingers and midfielders, and not just the defenders.
"Also, when we have the ball, we need to have confidence to play. We had space, and we used it very well in the first half."
Leko also praised the contribution of players who have not always featured regularly.
"We tried to freshen the team up a bit, especially with the wingers. I know that we will have space behind the full-backs and also in defence.
"We made some changes – I wanted to see the reaction of the players who maybe don't play as much. They showed that they deserve to carry the GNK Dinamo shirt. I think we represented Croatian football very well."
The victory lifted Dinamo to seven points in the league phase, although Leko is refusing to look too far ahead.
"We are now looking much better in the table with seven points, but still we go game by game."
The coach also thanked the travelling support after hearing his name chanted by the visiting fans.
"It's incredible, and I want to congratulate the players on a very good game, and also the fans who came here. I'm pleased that they're satisfied and they cheered my name. I appreciate that. We need to continue to work like this."