In a match that started two hours late because of rain in London on Friday (local time), Sun was able to lift her game again over the world No 61 when it mattered most and saved 15 of the 18 break points she had on her serve.
Sun is now the first New Zealand woman to reach the fourth round of the singles at Wimbledon since Ruia Morrison in 1959 and has now won six matches in a row at this year’s Championships, including three victories in qualifying.
“It was definitely tricky conditions today with the wind and waiting with the rain as well, and she’s a tough opponent,” Sun said.
“We had a lot of rallies as well as she had great service games. So it really came down to just a few points. During the tiebreak, exactly as I said, it comes down to a few points. So just really nailing it down to each point and fighting each point is what got me through.”
In the next round Sun will face Britan’s wildcard and US Open winner Emma Raducanu, who dominated Greek ninth seed Maria Sakkari, beating her 6-2 6-3.
Sun came back from being at 0-40 to hold in the second game and was also 15-40 down on her next service game.
Sun’s first break point came in the fifth game and she put in a disguised drop shot. Zhu ran in as quickly as she could but couldn’t get the ball over the net.
They swapped breaks later in the set, but when Sun served for it at 5-4, she had her only wobbly moment of the match, double-faulting three times.
However, in the tiebreaker, Sun got a mini break at 4-4 and Zhu put forehands wide to the right on the next two points.
Sun was broken in the opening game of the second set, but got the break back when Zhu was serving at 2-3. She also saved three more break points at 4-4.
So the match went to another tiebreaker, which was close all the way through.
But Sun got herself a match point on Zhu’s serve. The Kiwi pushed Zhu out wide to create the opening, got a short ball back and then hit it into the other corner for the winner.
This win is expected to lift Sun’s world ranking from 123 to 74 which means she will make it directly into the main draw at next month’s US Open.
She has also earned herself $471,000 in prize money by getting this far. Up to this week, the total prize money Sun had earned during her career was $277,000.
The 23-year-old only made her Grand Slam debut at the Australian Open this year, losing in the first round.
She pulled off a major upset on the tournament’s opening day, ousting Chinese world number eight Qinwen Zheng.