Coming together at 82-3 in the ninth over, the batters scored at just under 12 runs an over on a slow pitch to help England to a huge score of 221-3.
That partnership shows England's huge depth with the bat, with neither player guarenteed a starting berth when the T20 World Cup starts next month.
In reply, Pakistan lost four wickets in the powerplay. Thursday night's heroes, Babar Azam and Mohammad Rizwan, both fell cheaply for eight, as Mark Wood bowled well with searing pace in his first England game since March and his first T20I match since November 2021.
He finished with figures of 3-25 to show he is in the mix for the World Cup XI. Reece Topley was another to produce with the ball, going for just 22 runs from his four overs whilst picking up the prized scalp of Rizwan.
After the poor start, the hosts struggled to go up the gears and were never up with the required run rate.
Only Shan Masood showed any real resistance scoring 66 not out off 44 balls. Khushdil Shah also contributed, making 29 before being caught by Brook off Adil Rashid. Pakistan finished their 20 overs on 158-8.
Earlier in the game, England were ruthless with the bat scoring at 11 an over with a breathless display.
Alex Hales had been rested, with Will Jacks taking his spot as he was handed his first England start. Salt, who has opened all the games in the series, made eight before falling to Mohammad Hasnain early on. Jacks, though, looked assured, scoring at will in the powerplay with a strike rate of 181.
Dawid Malan - out for a golden duck on Thursday - laboured to 14 before being dismissed by spinner Usman Qadir. Jacks continued on his way before Qadir also saw the back of him for 40 - an innings that suggests a bright future in England colours for the Surrey slogger.
From then on it was the Duckett and Brook show. The pair scored at will, breaking England's highest partnership in the format and giving England an target that Pakistan never looked able to get near.
England now lead the series 2-1 with the fourth game of seven taking place on Sunday, again in Karachi. Check out all the stats from this fixture with Flashscore.
