After winning the toss and batting first at the Diamond Oval, the visitors amassed 290 for eight wickets.
Zondo struck 52 from 78 balls, Vaughn van Jaarsveld made 50 off 50 and Cody Chetty top-scored on his return to the team with 69 off 87 deliveries.
There were several other cameos from the Dolphins, including a three-ball 13 from Keshav Maharaj, who clubbed two sixes in his six-minute stay in the middle.
Shadley van Schalkwyk was the pick of the bowlers with three for 52.
Only 1.3 overs of the response were then possible when heavy rain stuck, forcing over two hours to be lost.
When the players return, the target was revised to 158 in 20 overs, but the switch to Twenty20 mode failed to ignite the hosts as they slipped to 111 all out in 18.3 overs.
They lost a wicket first ball and never recovered with Zondo returning the immaculate figures of three for 12 in 2.3 overs. Calvin Savage claimed three for 16 in his three impressive overs, while Maharaj picked up two for 19.
Van Schalkwyk top-scored with 34 off 20 balls for the Knights, whose chance of making the play-offs are all but over. They have eight points with three games to go, while the bonus-point triumph for the Dolphins lifted them to fourth.
Source: African News Agency (ANA)
