The always under-estimated Zimbabweans played a professional and disciplined cricket to reach the victory target of 235 with 24 balls to spare.
Their skipper Alister Campbell led from the front and with example by scoring an unbeaten 71 from 109 balls that included four boundaries.
Craig Evans belted three sixes and as many boundaries in his rapid 55 not out from 45 balls. The two shared in an unbroken 86-run sixth wicket partnership from 81 balls.
Karachi did well to reduce the tourists to 11 for two and then 90 for four, but never kept the flow of runs under check as the first 20 overs yielded 98 runs. And though the tourists needed 56 runs from the final 10 overs, Campbell kept on rotating the strike to Evans who wasted no opportunity of hitting big shots.
Campbell was lucky to survive when in 40s when Hasan Raza failed to hold a regulation catch at mid-wicket off Shahid Afridi. Probably, the ball might have hidden in the sun which was right into the eyes of the 18-year-old prodigy.
The only Zimbabwean loss from the match might be the cheap dismissals of Gavin Rennie and Murray Goodwin who failed to earn any significant batting practice for the one-day series starting at Gujranwala from Friday.
Rennie could score only five and Goodwin lasted for six balls before falling to former Pakistan Under-19 allrounder Kashif Ibraheem. Ibraheem finished with two for 59.
Flower brothers also blossomed with the bat. Opener Grant scored a 32-ball 26 with three fours and former captain Andy scored 36 off 50 balls with three fours. Both the batsmen fell to the crafty leg-spinners of Shahid Afridi who turned out to be the pick of home team bowlers with two for 36 from 10 overs.
Karachi, put into bat, were rescued by a defiant 101-run fourth wicket partnership between Sohail Jaffar and skipper Iqbal Imam after the first three wickets were down for 69 runs by the 11th over and the last seven wickets could add only 63 runs in 12 overs.
Jaffar, a discarded PIA stroke-maker, top scored with 63 while Imam, sacked by United Bank, scored a flawless 51.
Jaffar, the 29-year-old stylist batsman, struck four sweetly timed boundaries in his 109-ball innings to fully expose the talent and potential he has. Last season, he had scored over 500 runs in the first-class season while the year before, he had emerged as the top scorer with 1,400 first-class runs.
Imam continued his dazzling form by stroking five boundaries in his 88-ball innings. Imam, a utility cricketer who bats left-handed and bowls off-spinners, has so far scored 397 runs this season from eight innings including two centuries and a half century.
Jaffar and Imam repaired some damage after Test discard Shadab Kabir (3), Shahid Afridi (28) and Hasan Raza (10) had perished while playing some adventurous shots.
In the lower-order, Zafar Jadoon (19 off 15 balls) and Arif Mahmood (19 off 19 balls) tried to accelerate the proceedings but failed to counter the low trajectory spinners from Grant Flower. Flower, who had conceded 20 runs from his first five overs, bowled four overs in the slogging stages to not only give away 14 runs but also pick up four wickets to finish with four for 40.
It was chiefly because of Flower that Karachi could collect 57 runs in the last 10 overs.
Henry Olonga, who started with six no-balls in his first over, finished two wickets for 48 runs from six overs but turned out to be a shadow of himself who had demolished India last week in a Sharjah tournament match where he had figures of four for 46.