Cape Town - On a day when thirteen wickets fell, the Proteas will be glad for a healthy first innings lead after they ended the final session on 105/6.
After New Zealand were bowled out for 214 with Kane Williamson (77) standing out, the Proteas were looking to extend their already massive lead.
Quinton de Kock had licence to thrill at the top of the order and came out guns blazing, hitting Trent Boult's first over for four boundaries.
Boult and Tim Southee, however, quickly settled.
Boult trapped Stephen Cook (4) with a peach of a delivery while Southee removed Hashim Amla (1) soon after with another excellent ball.
JP Duminy (0) soon followed, trapped leg before by Southee while Proteas captain, Faf du Plessis was removed by Boult for six leaving South Africa at 47/4.
De Kock remained positive and together with Temba Bavuma posted a partnership of 35 before the left-hander could not get out the way of a Doug Bracewell lifter and fell caught in the slips.
Stiaan van Zyl (5) didn't last long either with first innings bowling hero Neil Wagner in on the action.
Despite the difficult second innings batting display, by the end of the day, the Proteas led stood at 372 and with the pitch very two-paced, New Zealand will face an uphill task to save the Test match.
Earlier, Dale Steyn (3/66 in 20 overs) and Kagiso Rabada (3/62 in 16.3 overs) were the main wicket takers for the home side.