A brace from man of the match Lerato Lamola, as well as an own goal from Carlington Nyadombo, secured all three points for the hosts, who played the majority of the match with a one-man advantage following Mbulelo Mabizela’s sending off in the opening period.
Siwele dominated the opening stages, as striker Lamola collected the second ball from a free-kick floated in from deep but could only find the side-netting with his shot from a difficult angle.
Their KZN visitors were quick to respond with chances of their own, but failed to produce any noteworthy danger on the opposition’s goal from a free-kick and corner in quick succession.
Celtic then upped the ante, as Keegan Ritchie fired a free-kick straight into the AmaZulu wall on 15 minutes, before good work by Musa Nyatama resulted in a perfect lay-off for teammate Lamola, who struck his ferocious effort well wide.
Lamola had another chance on 22 minutes, this time from a set-piece which lacked any real power as goalkeeper Energy Murambadoro easily gathered.
However, AmaZulu were then struck a major blow on the half-hour mark as new signing Mbulelo Mabizela struck out with his elbow at Alfred Ndengane, and referee Victor Gomes did not hesitate to show the former Black Aces defender red.
And just two minutes later, Celtic were ahead: great build up play on the left resulted in a fine save onto the post by Murambadoro from Mukuka Mulenga's shot, yet the ball fell kindly at the feet of the ever-present Lamola who slotted home his sixth League goal of the season.
AmaZulu’s only other chance of the half came through the left boot of Mark van Heerden, who struck his free-kick from just outside the box narrowly over the bar, as his side went into the break a goal down.
AmaZulu started the second half in the worst-possible fashion as Carlington Nyadombo headed past his own goalkeeper in an attempt to clear a cross from the right-hand side as Siwelele celebrated their second goal.
Steve Barker’s men were staring down the barrel just ten minutes into the second half as Keegan Ritchie’s free-kick struck a hand in the Usuthu wall, resulting in penalty for the home side.
After an infringement in the box, Lamola re-took the spot-kick, coolly slotting the ball down the middle for his second, and Celtic’s third, to take full command of proceedings.
Celtic dominated the rest of proceedings, coming close on numerous occasions as the visitors’ legs tired, being a man down.
The score remained unchanged for the rest of the half as Celtic secured an important victory, jumping five spots up the table to seventh, while AmaZulu remain rooted to the bottom, with just nine points from 18 matches.