Zampa bowled 10 wicketless overs for 113 – equalling the worst figures in an ODI, held by fellow Australian Mick Lewis – as Heinrich Klaasen propelled South Africa to their third-highest total.
Klaasen smashed 174 of just 83 balls as the hosts posted 416-5 at Centurion to level the five-match series 2-2, having lost the opening two.
Of greater concern for Australia will be the injury to opener Head, who retired hurt three balls after being hit on the left hand by Gerald Coetzee.
Australia coach Andrew McDonald confirmed x-rays had shown a fracture with the World Cup just three weeks away.
McDonald said: “He’s going to go in for some more scans tomorrow to work out the detail of (the injury) and then we’ll work out the management from there. How long that (recovery) time frame is, we’re yet to determine.”
Australia already have injury concerns over Pat Cummins, Steve Smith, Mitchell Starc and Glenn Maxwell, while Cameron Green was concussed in the first game of the series.
Klaasen described his assault, which included 13 fours and 13 sixes, as “one of my better ones”.
He was caught on the boundary off the final ball of the innings, ending a stand of 222 with David Miller who smashed an unbeaten 82 from 45. Rassie van der Dussen also hit 65.
Michael Neser was the only Australian bowler to go for under seven runs an over, Zampa conceding nine of the 20 sixes hit by the hosts
Australia’s reply never really got going, wicketkeeper Alex Carey the only batter to face more than 25 balls but he was last man out for 99 as Australia were dismissed for 252.
Set a target of 180, South Africa appeared to be in a strong position at 129 for 3 in the 14th over, but the West Indies bowlers had other plans. In a stunning collapse, South Africa lost seven wickets for just 20 runs within the space of 35 balls, eventually being bowled out for 149 in 19.4 overs, falling short by 30 runs.
The West Indies' innings was anchored by key contributions from Shai Hope (41) and Rovman Powell (35), allowing them to post a competitive 179 for 6. South Africa's bowlers, led by Lizaad Williams (3 for 36) and Gerald Coetzee (2 for 29), kept the West Indies' scoring in check, but the hosts managed a late flourish, adding 50 runs in the last five overs.
South Africa started their chase aggressively, racing to 100 inside 10 overs, but the West Indies bowlers tightened the screws in the middle overs. Akeal Hosein and Gudakesh Motie delivered crucial breakthroughs, dismissing Tristan Stubbs and Donovan Ferreira respectively. However, it was the duo of Romario Shepherd and Shamar Joseph who truly turned the game on its head.
Shepherd was particularly effective, claiming 3 for 15 in his four overs, while Joseph recorded a career-best 3 for 31. Their combined efforts derailed South Africa's chase, which at one point seemed on track for victory.
South Africa's middle-order collapse highlighted concerns for the visitors, with only one batter from No. 3 down managing to surpass 20 runs. In a match where individual scoring milestones were scarce, the West Indies' ability to clear the boundary made the difference. They hit 13 sixes compared to South Africa's six, underscoring their superiority in power-hitting.
The 47-run stand between Rovman Powell and Sherfane Rutherford provided the West Indies with a crucial edge, as their late acceleration ensured a challenging total for South Africa.
The victory not only secured the series for the West Indies but also demonstrated their growing dominance over South Africa, particularly in home conditions. The hosts will now look to build on this momentum as they prepare for future challenges.
The Unicorns won the toss in the winner-take-all encounter and decided to bat first.
Matthew Wade led the way with 49 while Chaitanya Bishnoi made 35 as the Unicorns posted 171-8 off their 20 overs.
Pacer Gerald Coetzee took 4-31 off his four overs for the Super Kings.
Texas then reached 172-7 with five balls to spare.
Milind Kumar set the foundation for the successful chase with a 42-ball 52 before Daniel Sams hit a whirlwind 18-ball 42 including two fours and four sixes to help seal qualification to the playoffs.
Haris Rauf and Shadab Khan each took a pair of wickets for the Unicorns.
The Seattle Orcas, Texas Super Kings and Washington Freedom have all confirmed their spots in the playoffs.
The final spot will be determined on Tuesday when the Orcas face MI New York. MI New York and San Francisco both have four points with New York ahead on net run rate. MI New York would seal their spot in the playoffs with a win or by avoiding a heavy defeat. If they lose by at least 130 runs, they would finish fifth and the Unicorns would advance.
