The 36-year-old made his first appearance for the Red Devils in more than seven months when introduced from the bench in Saturday evening's 4-1 win against Newcastle United.
Ibrahimovic, now sporting the number 10 shirt after re-signing for the club in the summer, battled back from a cruciate knee ligament injury well ahead of the predicted nine-month layoff.
Asked by BT Sport after the match if he was concerned about pushing himself too much, the Swedish striker said: "No. Lions don't recover like humans.
"This feels special. Different day, same quality. I'm not worried at all - I train hard, sacrifice a lot. I play in my head, my knee just needs to follow."
Ibrahimovic scored 28 goals in 46 appearances for United in his maiden campaign at United, leading to the offer of a new contract in August.