Published: 2017-10-31 22:53:00 BdST
The tourists have a lead of 48 with their marathon first innings having reached 150 overs and no sign of a declaration as they bat for time having won the first match in the two-test series by 117 runs.
Wicketkeeper Shane Dowrich is not out on his best test score of 75 and captain Jason Holder is 71 not out as the pair put on 144 for the eighth wicket.
Zimbabwe off-break bowler Sikandar Raza has been the chief wicket-taker with career-best figures of five for 82 from his 43 overs.
Resuming on their overnight score of 78 for one from 49 overs, the tourists quickened the pace, with Powell falling 10 short of a fourth test ton when he was brilliantly caught by Craig Ervine off the bowling of Christopher Mpofu.
At 230 for seven it looked as though Zimbabwe could force a first innings lead, but Dowrich and Holder steadied the nerves of the visitors and will now seek to build a sizeable lead on the fourth morning to bat their hosts out of the game.