Trailing 2-1 from the first-leg, Pohang dominated the return encounter at the Steelyard and went in front after nine minutes when Kim Jae-sung steered Jung Hong-youn's cross past Zob Ahan keeper Shahab Gordan.
Seol Ki-hyeon missed an empty goal in the second-half and Pohang were left to rue their wasted chances as Khalatbari, who was suspended for last week's clash in Esfahan, showed his class with ruthless efficiency as the Iran striker took his only chance of the game with 10 minutes to go.
Mahdi Rajabzadeh was sent-off three minutes from the end but Zob Ahan held on to go through 3-2 on aggregate.
Pohang held the upper hand for much of the first-half and they took the lead inside the first 10 minutes.
Mota (Joao Soares da Mota Neto) threaded a perfectly weighted ball inside the full-back to set Jung free down the left and his cutback from the byline was side-footed home by Kim, a member of Korea's World Cup squad, inside the near post.
Kim's goal levelled the quarter-final tie on aggregate and the hosts were now in line to go through courtesy of their away goal but Pohang continued to press for a second and Seol struck a fierce effort the wrong side of the near post in the 20th minute after being played in down the left-hand side of the box
Ahn Tae-un saw a long-range effort drift wide two minutes later before Zob Ahan called Shin Hwa-yong into action for the first time eight minutes before the break when Khalatbari's flick-on was turned over the bar by the Pohang keeper.
Seol had a chance to double Pohang's lead in the 59th minute when he smartly turned a defender outside the box but Zob Ahan keeper Gordan did excellently to come out and block his shot.
Seol was then guilty of an incredible miss 10 minutes later when a long ball down the left caught out the Zob Ahan defence leaving the former Al Hilal forward with a clear run on goal.
His first touch neatly took the ball past the onrushing Gordan but he then somehow conspired to blaze a left-footed shot over the bar from seven yards out with an empty goal at his mercy.
Seol's profligacy was made all the more acute with 10 minutes to go as Khalatbari levelled in clinical fashion with his first clear-cut opportunity.
The striker turned his man beautifully to receive Ghasem Hadadifar's pass, took one touch to get the ball out of his feet and drove a low right-footed shot across Shin and in off the far post to stun the boisterous home crowd.
Almir could not connect properly with a free header six yards out almost immediately after the goal before Rajabzadeh was booked for a second time with three minutes to go while off the pitch on a stretcher.
Although down to 10 men, Zob Ahan managed to withstand a late Pohang onslaught to book their place in the last four.