Playing as lone frontman, the Crystal Palace academy graduate, who is on loan at Selhurst Park after joining Manchester United in January, marked his seventh England U21s appearance with a superb first-half strike, jinking past a number of defenders before curling home.
Substitutes Jack Robinson and Nathan Delfouneso added extra gloss to what was an easy victory for England, who have now not tasted defeat since November 2011 and won eight on the trot without conceding a goal.
While the match may have ended comfortably, the start was a lot less straightforward. Henri Lansbury, making his first start for Pearce's side in more than a year, saw his night ended after just two minutes. The Nottingham Forest midfielder had burst down the right but came off worse in a challenge with goalkeeper Laurentiu Branescu, meaning Delfouneso was given an early introduction.
That bad start almost worsened soon after when Romania saw strong penalty appeals waved away after Craig Dawson and Andre Wisdom both handled in the box. It was a warning shot across the bows that England heeded as they took control of the game.
Raheem Sterling stung the palms of Branescu after fine work on the right by Zaha, before the Liverpool winger then forced the Romanian goalkeeper into action at his near post with a cross-shot. Zaha was the next to threaten the visitors' goal, only for Alexandru Cretu's head to block the striker's goalbound effort.
Romania were struggling to deal with England's attacking intent and, after Jonjo Shelvey saw 20-yard free-kick tipped behind, Sterling cut inside from the left before flashing a shot just over. The Young Lions' barrage continued as Delfouneso and Danny Rose had shots, before the opener came in the 34th minute.
Zaha collected a pass from Sterling and continued to skip past the Romanian defence, before curling a sumptuous strike into the top right-hand corner. It was no less than England deserved after an impressive first-half performance - one which the home side failed to continue into the second period.
The Young Lions were comfortable in possession but lacking a cutting edge, although Sterling came close after collecting a fine Jordan Henderson pass and cutting inside.
It was two other Liverpool players that combined to score England Under-21s' second of the night in the 61st minute. Shelvey sent a fine right-wing cross to the back post, where half-time substitute Robinson ghosted in to volley home.
A flurry of Romanian changes could not stem the tide as England came close to a third, with Zaha turning sublimely only to be denied by Branescu. Pearce made three changes for the final 16 minutes, with Tottenham's Tom Carroll coming on for his England Under-21 debut.
Marvin Sordell saw a shot deflect behind as England continued to press, before Delfouneso wrapped up a comfortable win with the hosts' third two minutes from time. He could have doubled his tally for the night in second-half stoppage time, but Branescu easily dealt with his late header.