Ngwenya has been Usuthu's standout performer this season, scoring nine goals in seven matches across all competitions. Seven of those goals have come in the Betway Premiership, with the striker finding the net in every league match AmaZulu have played.
His impressive start earned him the Betway Premiership Player of the Month award after scoring five goals in four matches in early September, helping AmaZulu climb the table.
Ngwenya continued his scoring run against Marumo Gallants last weekend, heading home at the back post to secure a 1-0 victory for AmaZulu.
Interestingly, Nkosikhona Radebe provided the assist, clipping the ball towards the back post for Ngwenya to finish.
Radebe and Mlondi Mbanjwa are the only other AmaZulu players to have scored this season, highlighting Zwane's concern over the lack of goals from other areas of the team.
"It is a worrying factor," said Zwane regarding having only one reliable goal-scorer.
"Before we even talk about the goals, we have to look at individual performances. When you face an opposition that is ready to defend and put their bodies on the line, you are going to face challenges if those clear-cut opportunities don't come easy."
Reflecting on their performance against Gallants, Zwane believes his players could have made better use of their opportunities.
"We had moments where we got the ball into the red zones and had chances to capitalise, but we were too hasty for no reason. It came down to poor decision-making."
AmaZulu have collected 13 points from six matches and are level with second-placed Orlando Pirates.
Zwane's side face Polokwane City at Old Peter Mokaba Stadium on Saturday.