Ashwell Prince scored his maiden century to give South Africa the upper hand after the second day of the second Test in Centurion on Saturday.
South Africa reached the close on 380 for six, a lead of 111 over Zimbabwe's first innings of 269.
Prince smashed an unbeaten 101 with 13 fours and two sixes.
Jacques Kallis, who scored 58, helped Prince add 119 for the sixth wicket after the South Africans had slipped to 219 for five.
Heath Streak was the pick of the Zimbabwean bowlers with two for 57.
Resuming on 13 without loss, South African openers AB de Villiers and Graeme Smith took their stand to 93 before Smith top-edged a pull shot off the bowling of medium pacer Elton Chigumbura to Barney Rogers at square leg.
Smith hit four fours and a six in his brisk 41, which he scored off 46 balls.
De Villiers was dismissed five overs later when he edged a drive off medium pacer Christopher Mpofu to Hamilton Masakadza at first slip.
De Villiers' 47 included seven fours and a six.
A dropped catch by Stuart Matsikenyeri gave Jacques Rudolph a life with the score on 111 but he did not survive for long as he was out just after lunch.
Rudolph (12) fell driving a delivery from leg-spinner Graeme Cremer on to his boot, from where the ball trickled on to his stumps.
Herschelle Gibbs and Prince stabilised the innings by adding 64 runs for the fourth wicket.
The partnership was ended when Gibbs top edged a paddled pull off Streak to wicketkeeper Tatenda Taibu, who made good ground to take the catch at short fine leg. Gibbs hit six fours and a six in his 47.
South Africa lost their fifth wicket six overs before tea after Mark Boucher drove a ball from Cremer to Masakadza at short cover to be dismissed for 18.
Prince and Kallis held sway with enterprising batting until the third over after the new ball was taken, when Kallis dragged a delivery from Streak on to his stumps. He faced 106 balls and hit five fours and two sixes.
Kallis batted at number seven instead of his usual number four position because he was off the field for much of Friday's play after injuring his right hip while bowling.
The all-rounder received a cortisone injection, which left him with double vision, team sources said.
Taibu injured his right shoulder while leaping to take a bouncer, and left the field after tea.
Brendan Taylor took over the wicketkeeping gloves in Taibu's absence.
Scoreboard:
Zimbabwe first innings: 269 all out
South Africa first innings: (13-0 overnight)
AB de Villiers c Masakadza b Mpofu 47
G Smith c Rogers b Chigumbura 41
J Rudolph b Cremer 12
H Gibbs c Taibu b Streak 47
A Prince not out 101
M Boucher c Masakadza b Cremer 18
J Kallis b Streak 58
N Boje not out 24
Extras (b-4 lb-4 nb-20 w-4) 32
Total (for six wickets, 91 overs) 380
Fall of wickets: 1-93 2-106 3-133 4-197 5-219 6-338.
To bat: M Zondeki, C Langeveldt, A Nel.
Bowling: Streak 15-1-57-2 (nb-1), Mpofu 17-1-68-1 (nb-9 w-1), Chigumbura 18-0-77-1 (nb-5 w-2), Cremer 26-4-105-2 (nb-3), Blignaut 14-0-59-0 (nb-2 w-1), Taylor 1-0-6-0.
Zimbabwe: S Matsikenyeri, B Rogers, H Masakadza, D Ebrahim, B Taylor, T Taibu, H Streak, A Blignaut, E Chigumbura, G Cremer, C Mpofu.
