Rio Olympian Brendan Irvine also qualified for the Worlds after earning a unanimous decision over Turkey’s Bathuhan Citfci to set up today’s flyweight quarter-final with Spain’s Gabriel Escobar.
But Tipperary super-heavy Dean Gardiner was TKO’d by Ukrainian super-heavy Viktor Vykhryst of the Ukraine.
McComb beat Dunaystev on a split verdict at Dublin’s National Stadium in April amid rumblings of “home town decision”.
But the Belfast light-welter did it again yesterday and it was once again apparent that the No. 1 seed was struggling against McComb’s tempo and slick counter-punching.
The top 8 boxers in each weight in Kharkiv qualify for the World Championships in Hamburg, Germany in August/September.
McComb will now meet England’s Pat McCormack in the last-eight tomorrow with a bronze medal up for grabs.
He said: “It was a tough and tricky fight having boxed each other just a few months ago, but I listened to Zaur in the corner.
“He had a plan and it worked very well.
“I haven’t got a chance to watch him (McCormack) out here. What I do know is he’s got as far so he must be doing something right, I will leave the plan to Zaur again and the rest of the team because I have trust in that.”
Joe Ward, the current European light-heavy champion, Darren O’Neill, Emmet Brennan and Kurt Walker are in last 16 action in Kharkiv today.
Meanwhile, ex-Irish head coach Billy Walsh, now chief seconds with USA Boxing, helped steer the USA to 14 medals – two gold – and six World places at the Americas Men’s and Women’s Championships in Honduras over the weekend.