Two-time world champion Zareen defeated the two-time Asian Champion Nguyen by unanimous decision.
In a rematch of the World Championship final, top Indian boxer Nikhat Zareen outclassed Vietnam's Thi Tam Nguyen 5-0 to move to the women's 50kg pre-quarterfinals while Preeti Pawar (54kg) sealed a place in the quarterfinals of the Asian Games in Hangzhou on Sunday. (Medal Tally | Full Coverage | More Sports News)
Two-time world champion Zareen defeated the two-time Asian Champion Nguyen by unanimous decision.
One of only four boxers to not get a first-round bye in the 50kg event despite being the reigning world champion, Zareen controlled the proceedings from the word go.
"I had not expected it (to be a one-sided bout) but my plan was to make it one because it's happening in another country and I didn't want to give any chance to her. My plan was to win the first two rounds unanimously and then relax in the third," Zareen said after the win.
In the opening two rounds, Zareen landed accurate punches, rattling her opponent.
Such was her power that the referee was forced to give Nguyen the eight count twice in 30 seconds in the opening round.
Nguyen tried to attack in the second round but Zareen retaliated with strong combination punches, forcing a third eight-count upon the Vietnamese boxer.
With her work done, Zareen conserved energy in the final three minutes, defending beautifully with the help of her nimble footwork.
With coveted Olympic quotas at stake, Zareen said she is concentrating on qualifying for the Paris Games first.
"I am focussing on qualification first. Then step by step I'll think of final and gold," Zareen said.
All four semifinalists in the light flyweight category will earn Olympic quotas.
Also Putting up a dominating show was talented Indian boxer Preeti, who notched up an RSC (referee stops contest) win over Jordan's Silina Alhasanat.
Zareen will face Chorong Bak of South Korea in the Round of 16 while a tough bout awaits Preeti. The Indian teenager will have to fight seasoned Kazakh boxer and three-time world medallist Zhaina Shekerbekova
The 19-year-old Preeti, who made the pre-quarterfinals of the World Championships earlier this year, is now one bout away from assuring herself of a medal and an Olympic quota.
Playing a strategic bout, Preeti started the contest in a defensive mode before unleashing her attacking game.
After a sedate start, the Indian went on the offensive and landed perfect jabs and hooks to win the opening two rounds easily.
After showing promise initially, Silina faded away and looked at sea as the referee gave her two standing counts in the second and third rounds before stopping the contest.