Among other Indians in the competition, four-time Asian medallist Shiva Thapa (63kg) got a bye into the second round.
In women's events, the semi-finalists in the 50kg, 54kg, 57kg, and 60kg as well as the finalists in the 66kg and 75kg will qualify for the Paris Olympics.
Deepak clinched one of the most memorable wins of his career with a 4-1 win over more fancied Zoirov
Tokyo Olympian and 2019 Asian Championships silver medallist Ashish Chaudhary will also be representing the country for the second time and would be keen to add another major medal to his name.
Nitu beat Italy's Erika Prisciandaro, a former Youth World Championship bronze-medallist, 5-0, while Zareen outpunched Ukraine's Tetiana Kob, a three-time European Championships medallist, 4-1.
Zareen won the bout after local favourite and former champion Sevda Asenova abandoned the contest during the opening round.
A summary of sports events and persons who made news on Wednesday.
A summary of sports events and sports persons, who made news on Sunday
A summary of sports events and persons who made news on Monday
A summary of sports events and sports persons, who made news on Saturday.
A summary of sports events and sports persons, who made news on Friday
A summary of sports events and persons who made news on Thursday