Ibrahimovic, 35, opened the scoring in the 30th minute of Sunday's game at the Stadium of Light, rolling Billy Jones and crashing a shot into the bottom corner from the edge of the box. United went on to win 0-3, maintaining pressure on Manchester City, and heaping further misery on Sunderland.
Ibrahimovic feeling fresh
"The older you are, the more experienced, the more intelligent and you don't waste energy on things you don't need," Ibrahimovic mused after the match.
"I feel like Benjamin Button. I was born old and will die young," he added, citing the 2008 Brad Pitt film about a man who ages in reverse.
Ibrahimovic recently claimed that Manchester United's players are letting Jose Mourinho down, as the club endure an uninspiring season.
Mourinho full of praise
United manager Jose Mourinho said: "You need these players to break it. Every team has a couple of them. Zlatan did that."
Victory saw United close to within four points of Manchester City, who occupy the fourth and final Champions League qualifying berth and have played a game more than Mourinho's side.
"The result was good," Mourinho said, "we resisted the results of yesterday when Manchester City and Liverpool won. They left us in a position of 'yes' or 'no'. It was 'yes'."
The result left Sunderland 10 points adrift of safety at the foot of the table and Mourinho said they had played like a team who were "close to relegation".