Chennai, Feb 6 - Naman Ojha (104) and Robin Bist (104 not out) helped themselves to centuries as the Central Zone took a decisive step towards a berth in the final of the Duleep Trophy with an overall lead of 488 by close of play on the penultimate day of their semi-final match against South Zone here Monday.

Having gained a first innings lead of 110, the Central Zone, overnight 127 for one, piled up 378 for five in their second knock as South bowlers toiled for little rewards.

A 140-run partnership between Ojha and Mohammad Kaif (43) for the second wicket followed by an unfinished 160-run association involving Bist and Bhuvnesh Kumar (59 not out) featured the third day's play that saw South Zone, after an early strike, going through the motions.

South began the day on a promising note, dismissing first innings centurion Kaif who added just two runs to his overnight score of 41. Kaif top-edged a pull off Abhimanyu Mithun to mid-wicket where Amit Verma took a brilliant catch, with the ball coming from over his shoulder.

Mohnish Mishra was lucky to survive a confident appeal for leg-before when Mahesh rapped him on the pads with a delivery that ducked back in while Ojha went into his shell approaching the hundred mark.

It allowed the South Zone bowlers to get back on top while their seamers showed greater discipline to stick to stump-to-stump line. However, the introduction of left-arm spinner K. P. Appanna loosened their hold on the batsmen.

The spinner came in for some stick, especially at the hands of Mishra, while Ojha, looking rather subdued, was dismissed soon after he got to his century when he was castled by Stuart Binny who was brought on just before the lunch break.

In the very next over, Appanna dismissed Mishra (33) who was beaten by the flight and holed out in the deep where Manish Pandey took a well-judged catch, running to his right.

Thereafter, Central batsmen made no haste with an obvious intention of setting a huge target while the South Zone players also did not show any urgency as the proceedings drifted along at a sedate pace.

Post lunch, Central lost Parvinder Singh (17) who became Binny's second victim and the Karnataka seamer was the pick of the bowlers, sticking to a fuller length while occasionally troubling the batsmen with the one that moved off the seam. Surprisingly though, he was used rather sparingly.

Bist and Bhuvnesh Kumar then pressed on, grinding a progressively dispirited South Zone bowling into total submission as Central moved into an unassailable position by stumps.

Brief Scores: At Chennai: Central Zone 293 and 378/5 in 122 overs (Naman Ojha 104, Robin Bist batting 104; Stuart Binny 34-2, Abhimanyu Mithun 60-1) vs. South Zone 183 (IANS)