The duo chased down UAE's competitive target of 174 with more than four overs to spare, their unbeaten partnership of 175 eclipsing the record for the highest stand for any wicket at the men's T20 World Cup.
Seifert finished unbeaten on 89 and Allen 84 as New Zealand romped home in just 15.2 overs to top Group D with a display of power-hitting that left UAE's bowlers shell-shocked.
New Zealand raced to 78-0 in the opening powerplay, with Seifert and Allen dispatching the ball to all corners of the ground.
Although spinner Haider Ali managed to stem the flow with just eight runs from his first two overs, fast bowlers Muhammad Rohid and Junaid Siddique had no such luck as the openers attacked them when they bowled length deliveries.
Seifert reached his half-century in 23 balls - his second fifty of the tournament after his 65 against Afghanistan - and Allen matched him stride for stride as the pair guided New Zealand to the finish line.
The demolition job was completed in emphatic fashion when Seifert smashed a six down the ground.
Waseem's heroics with the bat
Earlier, UAE captain Muhammad Waseem had given his team hope with an unbeaten 66 after winning the toss.
Despite losing opener Aryansh Sharma early when he skied a short Jacob Duffy delivery to long leg, Waseem and Alishan Sharafu rebuilt with a 107-run partnership off 77 balls.
The pair scored runs to all corners of the ground, especially behind the wicket when they used the bowlers' pace to clear the infield and find the boundary.
Sharafu made 55 before falling to a spectacular boundary catch, where Mark Chapman leapt into the air and caught the ball but as he fell over the boundary he quickly tossed it into the hands of Glenn Phillips.
Waseem reached his fifty in 37 balls and Phillips conceded 27 runs in the 18th over, but New Zealand stemmed the flow of runs with three wickets at the death to restrict UAE to 173-6.