The twice collegiate champion turned professional 10 days ago after 141 weeks as the world's top-ranked amateur and sealed the title with a tap-in for par at the second play-off hole at New Jersey's Liberty National Golf Course.

"What is happening? I just can't believe it," she said in a greenside TV interview. "It was just last week that I won NCAAs with my team-mates and to turn pro and come out here, it's just been amazing."

Zhang had a two-shot lead through 54 holes and could have avoided the playoff were it not for an errant putt that saw her stumble into a bogey on the final hole.

But the 20-year-old Californian showed poise well beyond her years when she drained a six-foot putt on the first playoff hole and set herself up for success with a brilliant approach shot on the second.

"This golf course is rough, I really got a bit of everything. Got a taste of the pressure, got a taste of the wind and I tried to stay composed as always," said Zhang.

"I knew that golf was just a grind and you really have to dig deep so that's what I did once again."

Zhang, who won the Augusta National Women's Amateur in April, is the second woman to win in her pro debut on the tour after Beverly Hanson in 1951.

"I want to continue trying to carve a path for young kids to just follow their dreams," she added. "I will continue to do what I'm doing, I'll continue to fight."