Kyrgios brushed aside seeded Italian Fabio Fognini 6-2 6-4 in just 61 minutes before Kokkinakis needed almost three hours to shake off American Denis Kudla 7-6 (7-5) 4-6 7-6 (7-4).

His serve mostly untouchable in recent times, Kyrgios surprised even himself with the new heights he reached this match.

The dual grand slam quarter-finalist conceded a meagre eight points in nine service games.

"Wow, I felt like I was a bit hard on myself now. I thought I didn't serve that well for some reason," Kyrgios said.

"I guess it's just high standards. I want to keep that momentum from the last match (against Andrey Rublev) going.

"As soon as I had some break points, I wanted to take them early then Fabio can get a bit disinterested when things aren't going his way."

The victory improved his 2022 record to 7-2 after Kyrgios arrived in Miami on the back of a run to the quarter-finals at Indian Wells.

And Kyrgios credited his increased doubles workload, including partnering Kokkinakis to the Australian Open title in January, for his surge in singles form.

"Doubles, I don't give enough credit to doubles. That's helped me a lot, and Thanasi as well," he said.

"We're both returning a lot better on the singles court.

"The way I'm serving, the way I'm returning and working the points and competing, it's quite a sight to see."

Kyrgios next faces world No.11 Jannik Sinner, a 5-7 7-5 7-5 winner over the 19th-ranked Pablo Carreno Busta, for a spot in the quarters.

Kokkinakis followed his Australian Open doubles-winning partner into the last 16 with a spirited display against Kudla.

He stood three points from losing the marathon encounter before pulling out an important win that set up a showdown with German second seed Alexander Zverev.

Win or lose their next matches, Kyrgios and Kokkinakis are now assured of both being in the world's top 100 again for the first time since August of 2016.

"It's awesome to see," Kyrgios said of Kokkinakis' stunning renaissance following years of endless injuries.

"I see him in the locker room and having lunch and just see a happier person. I don't really care about results and all that, I know what he's capable of, I've grown up with him.

"To see him finally happy and not in those dark places where he was struggling with his body, whether he was even thinking about playing again - they were some scary thoughts.

"I saw him go through that. Just seeing him happy again and being at these big events and winning, that's all I care about. Not his results."

Australian Associated Press