Having raced into an early lead at the Arms Park, Cardiff then found themselves trailing midway through the second half following a 20-minute red card for Wales centre Ben Thomas.
But they rallied in the rain to claim a 33-20 bonus point victory, with two tries from replacement hooker Evan Lloyd off close-range line-outs sealing the spoils.
“There were a few rollercoasters in that game,” said former Italy second row Van Zyl, who has stepped up following Matt Sherratt’s eve-of-season exit to join Wales.
“We started really well and had the momentum, but the red card was a big turning point. We struggled a little bit after that with managing the game.
“So, it was a real good rollercoaster, but ultimately what counts is the boys stuck to it and got it over the line. There was good leadership from the senior players on the field.
“We got back in front and then put the pressure on. There are a few things we can do better, but the fight was definitely there. It’s a win, let’s move on.”
Van Zyl was full of praise for No. 8 Alun Lawrence, who topped the carrying (16) and tackling (12) stats to earn the Player of the Match award.
“He’s an unbelievable machine. He’s got an engine on him and he’s so consistent,” he said.
For the South African-born Van Zyl, it was a first game at the helm following the departure of Sherratt.
“I was a little bit more nervous than usual,” he admitted.
“When you need to make the calls, you think of all the things that can happen, and you have to be smart in your decisions, instantly.
“So it was different, but very enjoyable. I loved it. Obviously, the win helps!”
Giving the players’ perspective, second row Josh McNally said: “With losing Matt at the start of the week, the other coaches have all stepped up and it’s been an excellent environment.
“We wanted to get onto the pitch and put a performance down, and I am just so proud of the boys. Everyone put a huge shift in. We stuck to our processes and got a decent five-point win.”
The other three Welsh teams were beaten, but there was a notable achievement from the Ospreys, who scored six tries against the Vodacom Bulls at Pretoria’s Loftus Versfeld.
They led 26-12 at one stage, while there were two tries apiece from centre Keiran Williams and wing Keelan Giles.
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But, in the end, they went down 53-40 with hooker Johan Grobbelaar scoring a hat-trick for the powerful Bulls.
Ospreys coach Mark Jones said: “It smarts a little bit.
“With the way we played in the first half, we looked deserving of the lead. We put a decent marker on the ground in terms of how we want to play the game with the ball.
“But we had moments of self-harm with how we encouraged the Bulls into our red zone and they really picked on a lot of our errors and scored.
“We spent too much time without the ball and when you do that against South African teams, it’s always difficult.”
Skipper Dewi Lake added: “There were a massive amount of positives for us.
“To come to Loftus and score 40 points is an immense display of attack, but to also concede 53 is tough to take.
“Physically, we stepped up, we matched the physical battle around the park.
“But set-piece probably let us down. We didn’t really get a foothold in scrum and lineout, and it’s tough to get possession and territory and get yourself into the game then.”
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While there was only the one Welsh win, there were encouraging signs from an attacking point of view, with the four regions scoring 17 tries between them.
The Scarlets were beaten 34-21 at home by Munster, who secured a bonus point, while the Dragons were well-beaten, 42-21, at Ulster.
It’s Round 2 next weekend, with three games on Friday, four on Saturday and one on Sunday.
There’s just the one match featuring two winners from the opening round, as Munster host Cardiff at Limerick’s Thomond Park.
Leinster will be looking to bounce back from their heavy defeat in Cape Town, but things don’t get any easier for them as they face another major challenge on South African soil with a trip to Pretoria to face a Vodacom Bulls team that racked up nine tries in Round 1.
Elsewhere, it’s DHL Stormers v Ospreys, Dragons v Hollywoodbets Sharks, Edinburgh v Ulster, Connacht v Scarlets, Benetton v Glasgow Warriors and Zebre Parma v Lions.
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