Towhid and Zakir joined hands at the middle in the fifth over and batted together for 65 balls where the duo added 114 runs.
Towhid, the aggressor of the two, hit nine fours in a masterful innings while Zakir hit two fours and cleared the ropes for six runs four times.
Pacer Nahid Rana broke the rollicking partnership by getting Towhid caught at extra-cover in the 16th over.
The following over, Zakir also followed him to the dressingroom after getting bowled by Nahidul Islam.
After losing two set batsmen in quick succession, Sylhet were at risk of floundering in the final overs.
But Zimbabwean batter Ryan Burl (21 off 11 balls) and Sri Lankan all-rounder Thisara Perera (17 off seven balls) made sure that Sylhet would finish with a flurry and post a daunting total for Khulna.
Earlier, Khulna won the toss and asked Sylhet to take first strike.