Sun, who was born in Te Anau, defeated the pre-match favourite, Britain's Emma Raducanu 6-2 5-7 6-2, earning her a spot in the quarterfinals.
She is the first New Zealand woman to reach the last eight at Wimbledon. Before this match, the last Kiwi singles player to reach the last 16 at a grand slam was Brett Steven in the men's singles in 1997.
Shawn Sage-Cleaver from Tennis NZ told Morning Report the win was hugely exciting.
"This is an incredible day for Lulu. An incredible day for New Zealand tennis as well."
Sun had been "knocking on the door for a while", Sage-Cleaver said, and her win showed that "anything really is possible".
It was also exciting for New Zealand tennis to have success in the singles competition, he said.
"It's really monumental ... we're super-stoked for Lulu."
Over the past few years, doubles players - such as Michael Venus and Erin Routliffe - had enjoyed well-earned accolades, but "it's just really awesome to have some of that success as well on the singles side".
Sun left Aotearoa for Switzerland as a child, but in March switched allegiance to play for New Zealand.
The move saw her immediately become the country's top-ranked player.
Sage-Cleaver described her game as "aggressive", especially on a grass court.
But it was her determination that he most admired, he said.
"Really it's a mental tenacity and her grit."
He noted that Sun had hit 50 winners over the course of today's match. He believed three-set matches during her qualifier campaign, which also included saving a match point, helped build her mental resolve.
Next, Sun will face Croatia's Donna Vekic in the quarterfinals on Tuesday (UK time).
Sage-Cleaver said Sun and Vekic had similar stories, in that they had both flown "a little bit under the radar".
The quarterfinals would be a "good opportunity", he said, but he did not want to focus on that at this stage.
"We're not too concerned with that round yet, because we really want to celebrate today and mark the significance of this one, making it into the quarterfinals."
Since Sun switched her allegiance from Switzerland to New Zealand the national body has been providing her with "administrative support" as well as funding to help with her coaching and physios.
Sage-Cleaver said the player was impressed with the support she received at the ASB Classic in Auckland in January.
