Commonwealth Games gold medallist Amit Panghal and national champion Sachin entered the semifinals of the 75th Strandja Memorial boxing event in Sofia, Bulgaria.
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.
Among other Indians in the competition, four-time Asian medallist Shiva Thapa (63kg) got a bye into the second round.
Continuing that momentum, Hussamuddin took charge of the final round as well, and secured a 4-1 victory.
World Championship medallist Amit Panghal and Sachin Siwach struck gold at the 75th Strandja Memorial tournament.
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 sports persons, who made news on Sunday
Nikhat, Jaismine and four other Indian boxers march into finals
In the other semi-final bouts, S Kalaivani, Shruti Yadav, and Monika suffered identical 0-5 defeats and bowed out of the competition.
Anamika, the reigning national champion, lost by a 1-4 split verdict against China's Hu Meiyi in the lightweight final.
The Boxing Federation of India (BFI) is conducting the men's national championships in Bareilly in 10 weight categories
Boxing Federation of India president Ajay Singh on Thursday asserted that boxers will not miss any more tournaments, with national camps set to resume soon and a new coaching setup also to be announced.
Two-time world champion boxer Nikhat Zareen isn't fazed by the prospect of facing tough opponents early in her Olympic debut
Despite delays in the BFI's elections, which are currently stalled due to ongoing court cases, Singh confirmed that the federation will proceed with appointing the new coaching staff to ensure that boxers are not impacted.
Naveen Boora in medal rounds of Strandja Memorial tourney
Indian pugilists will be determined to overcome the recent setbacks both inside and outside the boxing ring when they aim for the last available tickets to the Olympic Games at the second World Qualification Tournament, starting in Bangkok on Friday.
Commonwealth Games gold medallist Amit Panghal, national champion Akash and Abhimanyu Loura put up a stellar show to move into the quarterfinals of the 75th Strandja Memorial Tournament in Sofia, Bulgaria on Wednesday.
Two-time world champion Nikhat Zareen (50kg) bowed out of the Olympic Games after a shock defeat to Asian Games gold-medallist Wu Yu of China on Thursday.
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.
World championship trials would be held from March 7 to 9, followed by the Asiad trials from March 10 to 13.
Nitu (48kg) and Jasmine (60kg) were the others boxers who sealed spots for the quadrennial event, in Birmingham from July 28 to August 8.
Dominant efforts by two-time world champion Nikhat Zareen and Commonwealth Games gold medallist Amit Panghal headlined Indian boxers' march into six finals at the 75th Strandja Memorial Tournament in Sofia, Bulgaria on Saturday.
Two-time World Champion Nikhat Zareen eked out a gritty win while Arundhati Choudhary too won her bout to advance to the semifinals of the 75th Strandja Memorial Tournament in Sofia, Bulgaria on Thursday.
World Championships silver medallist Amit Panghal qualified for the Paris Olympic after defeating China's Chuang Liu in the 51kg quarter-finals of the second World Qualification Tournament in Bangkok on Sunday.
Nikhat's form augurs well for India with the Olympics coming up next year.
The 34-year-old, a five-time World champion and an Olympic bronze-medallist, struggled to connect clean punches against her taller rival and was even warned once for excessive bending.
Amit Panghal will be eager to exorcise the ghosts of disappointing Tokyo Games
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.
The Asian Games gold medallist was nominated last year as well but was not considered due to a failed dope test in 2012, for which he served a one-year ban.
The Indian boxer defeated Tanzania's Haruna Mhando by a unanimous verdict.
Deepak clinched one of the most memorable wins of his career with a 4-1 win over more fancied Zoirov
Earlier, another debutant Rohit Mor (57kg) gave India a winning start by sailing past Ecuador's Jean Caicedo 5-0 in a confident opening-round performance on Tuesday. Next up for him is Bosnia and Herzegovina's Alen Rahimic.
International-medallist Deepak Kumar (51kg) led the show as Services Sports Control Board (SSCB) boxers produced an impressive all-win performance on the second day of the men's National Championships at the Inspire Institute of Sports in Bellary on Thursday.
A summary of sports events and persons who made news on Wednesday.
In the ongoing Women's World Championship, Jaismine Lamboria clinched her opening bout on Friday.
India would be aiming to better their best-ever show when the trio of Deepak Bhoria, Mohammad Hussamudin and Nishant Dev step inside the ring in pursuit of summit berths in the men's boxing World Championships.
The 23-year-old Naib Subedar in the Indian Army said the Pulwama terror attack, which claimed the lives of 44 CRPF personnel, was on his mind through the tournament.
The diminutive Manipuri became the most successful boxer in world championships' history when she claimed the 48kg category top honours in November last year in Delhi.
The legend of M C Mary Kom (48kg) grew larger as she added the Commonwealth Games gold to her packed medal cabinet, thrashing Northern Ireland's Kristina O'Hara in the final, in Gold Coast, on Saturday.
International medal-winning Indian woman boxer Neeraj (57kg), who was among the probables for 2020 Tokyo Olympics, has been provisionally suspended after failing a dope test.