Usuthu were in crises mode going into the match without a win in six, but after weathering an early storm, an own goal from Nazeer Allie set them on their way, before former Ajax striker Stanton Lewis netted a brace and Tangeni Shapahu scored as well.
Ajax started the brighter but were behind on the 20 minute mark after a disastrous piece of play.
Aiden Jenniker’s backpass was far too short for goalkeeper Sean Roberts and Ayanda Dlamini latched onto the ball. He rounded Roberts and although his shot came back off the post, it struck the unlucky Allie and went into the net.
The goal gave the home side confidence and they began to boss the midfield battle.
They were 2-0 up just past the half-hour mark as Dlamini produced more fine work down the left and his cut-back for Lewis was perfect, allowing the former Ajax man to fire the ball home.
Granwald Scott almost pulled one back for Ajax just after halftime when he saw his effort brilliantly saved by Mbongeni Mzimela.
Terror Fanteni had the ball in the back of the net on the hour-mark, but the effort was ruled out for offside.
But Usuthu extended their lead with 20 minutes remaining when Shipahu was sent clear by Thamsanqa Sangweni and he finished low past Roberts.
And it was 4-0 just two minutes later when Lewis netted his second of the night after racing through the shattered Ajax defence to score.
Ajax might have restored some pride as Lebohang Manyama tested Mzimela, but the Usuthu goalkeeper was again in inspired form.
The win moves AmaZulu up to 13th, for 24 hours at least, above Black Leopards on goal-difference.