The goals came from Ayanda Dlamini (2) and Lehlohonolo Majoro for AmaZulu in the first half.
United’s goals came from Rudolph Bester and an own-goal by Siphiwe Mkhonza.
The scores were tied at 2-2 with seconds remaining, but a piece of individual brilliance from Dlamini earned the Usuthu a deserving haul of three points.
After a tentative start from both teams, Dlamini gave Amazulu the lead when he flicked Ntokozo Sikhakhane’s free-kick beyond Shu-aib Walters in the 12th minute.
United also profited from a set-piece, when Kurt Lentjies drilled a ball into the AmaZulu penalty area which goalkeeper Mbongeni Mzimela palmed into the path of Rudolph Bester; the striker fired home a powerful strike from close range.
AmaZulu generally showed more attacking intent in the first half with their wide players, Majoro and Sibusiso Hadebe, causing a few anxious moments for opposing defenders, while the visitors preferred to wait patiently to string counter-attacking moves.
A few minutes before the interval Majoro got his name on the scoresheet when he headed authoritatively past Walters after Sikhakhane picked him out with a well weighted cross.
The vistors were back on level terms shortly after the break when AmaZulu’s midfield anchor Mkhonza sent a back-pass beyond the reach of his own goalkeeper and into the net.
In the 64th minute, Walters was in the thick of the action yet again. Majoro hit a cracking drive from near the edge of United’s penalty area which the keeper kept out with an outstretched boot.
Litha Ngxabi, who was following up, rifled a thunderous effort which crashed onto United’s crossbar, Walters was on hand to collect the rebounder.
A minute later, Mzimela was required to be at full stretch to keep out the Kurt Lentjies stinging low drive.