"Both of them, they keep on improving each game they play," Dhoni told reporters.

"They look to improve. They raise the bar wherever they are performing."

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Gambhir was the top-performing batsman of the tour, despite having only cemented his place in the Test side after a strong series against Sri Lanka in the middle of last year and a barrage of runs since.

His second innings 137 in the second Test in Napier guided India to the safety of a draw after New Zealand ran up a massive 619 for nine in the first innings and dismissed the visitors for 305 in their first knock.

Gambhir's second innings 167 in Wellington set India on the path to victory, which was only thwarted by rain on the last day.

By the end of the Test series, he had accumulated 445 runs at an average of 89.0, eclipsing the effort of the "Little Master" Sachin Tendulkar who finished with 344 runs at an average of 68.8.

Master off-spinner Harbhajan Singh finished the series with 16 wickets at an average of 21.37 runs per wicket. His best innings saw him grabbing six wickets for just 63 runs.

Left-arm pace bowler Khan was second in India's bowling ranks, garnering 13 wickets at an average cost of 30.76 runs in the three-Test series, including a best performance of five for 65 in New Zealand's first innings in Wellington.

"Zak (Khan) has been brilliant for the last two years. He has bowled well everywhere, not only India," Dhoni said.

"He helps the other bowlers and it has been fantastic to see the way he has bowled, whether the wicket is helping him or not."

But Dhoni said the whole team deserved the credit for the long-awaited series win.

"It was a very good team effort. The batsmen and the bowlers contributed when it was needed from them.

"I think the overall effort by the bowlers was great."

He also praised the work of the lower order batsmen, who were instrumental, particularly in Wellington where India were 204 for six in their first innings before a late rush of runs took them to 379.

"The lower order contribution was very important because that really takes the morale of the team up, and whenever it was needed from them, the lower order really contributed."