Cook moved on to 69 at the interval with Root on 58 and England led by 41 runs with seven wickets in hand and five sessions of an intriguing match remaining.
Ian Bell was out to the third ball of the day for 29, pushing tamely at a wide ball from Tim Southee and edging the ball to wicketkeeper Tom Latham.
Cook, 32 not out overnight, defended resolutely and brought up his fifty off 122 balls while Root struggled to find the sweet timing he showed in making 98 in the first innings.
The New Zealand pace bowlers beat the bat a few times but Root remained unruffled, reaching his half century by sweeping spinner Mark Craig for his seventh four.
Root survived a huge shout for lbw off Trent Boult in the last over before the interval following an unsuccessful review by the New Zealanders. – Reuters
Original source: Cook, Root lead England revival