Irish forward power and a class half-back combination between Dolphin's Pat McCarthy and Galwegians' Gavin Duffy was more than enough to seal this match by half time at Dr Hickey Park on Saturday.
Outhalf Duffy scored a splendid try from just within his half, outwitting three desperate tackles on his way, to give scrumhalf McCarthy an easy conversion.
McCarthy had earlier scored a penalty and added two more and two conversions to bring his tally to 13 for the match. Shannon's centre and Irish captain, Mossie Lawlor, finished off another superb break and long pass by Duffy to score Ireland's second try.
The result became certain when second row Matthew McCullough surged through a hole in the New Zealand defence after the Irish forwards had shown the All Blacks what forward play was all about.
A lapse in Irish concentration immediately into the second half allowed New Zealand flanker Scott Waldrom in for an easy try far out, but a seamless defence and crunching tackles, particularly by winger Gary Brown of Blackrock and Fiachra Baynes of Greystones, held the New Zealanders at bay.
A final penalty from McCarthy added the icing to a very well made cake.
Aayden Clarke added a compensation penalty for the visitors in the first half.
IRELAND U-21: G D'Arcy; J Norton, K Lewis, M Lawlor (capt), G Brown; G Duffy, P McCarthy; R Flanagan, G Hickie, N Treston, D O'Callaghan, M McCullough, N Breslin, J O'Connor, D Dillon. Replacements: S Keogh for Lawlor; F Baynes for D'Arcy; D Browne for McCullough; N Foxe for Flanagan.
NEW ZEALAND YOUTHS: T Manawata; K Andrews, D Bell, G Clarke, R Wynen; A Clarke, J King (capt); T Hunt, L Mahoney, R McKinney, J Saipani, B Taylor, C Hunter, S Waldrom, S Kepu. Replacements: N Edmonds for G Clarke; B Williamson for Waldrom.
Referee: T Spreadbury (England).
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