Aces, who had goalkeeper Jackson Mabokgwane sent off in the 65th minute, prevailed via goals from Tendai Ndoro, S'boniso Gumede and Eddie Ngalo, while Goodman Dlamini netted for the hosts at Princess Magogo Stadium.
The match pitted AmaZayoni boss Clive Barker against his nephew Steve for the first time since the latter took charge of Usuthu late last month.
Victory lifted Aces to sixth on the Absa Premiership table with 20 points from 14 games - 16 points adrift of leaders Kaizer Chiefs, and 13 points ahead of AmaZulu.
AmaZulu had the first shot in anger, with Tshepo Liphoko getting an effort on target in the fifth minute, but Mabokgwane made a comfortable save.
The teams went on to trade chances throughout the first half, with strikers Bornwell Mwape and Bongani Ndulula looking dangerous for the home side, while Aces’ Ndoro and Collins Mbesuma were a genuine threat.
In fact, Ndoro was the man who opened the scoring just before half time. The Zimbabwean striker scored direct from a free-kick to put the visitors ahead.
Shortly after the restart it was 2-0 to AmaZayoni, as defender Gumede headed home from an Onyekachi Okonkwo corner.
AmaZulu reacted by shifting their formation, sending on Ayanda Dlamini and Carlington Nyadombo from the bench.
The former made an immediate impact, setting up his namesake G. Dlamini to score past Mabokgwane and reduce the deficit to 2-1 in the 55th minute.
However, on the hour-mark, Aces restored their two-goal lead. Ngalo got on the end of Aubrey Ngoma’s corner and headed home the visitors’ third goal.
The match took yet another twist soon after as Mabokgwane received a second yellow card for time-wasting and was sent off for an early shower.
With a numerical advantage, AmaZulu dominated the remainder of the match, but they were unable to find a way through Aces’ defence and substitute keeper Energy Murambadoro.