Saturday's win ensured all three Saudi Pro League sides reached the semi-finals.
The 40-year-old Ronaldo scored his eighth goal of the tournament during a dominant first half performance in Jeddah, which is hosting all of the games in the tournament from the quarter-final stage to the final on May 3.
In Wednesday's semi-final, Al-Nassr will take on Al-Sadd of Qatar or Kawasaki Frontale of Japan, who meet on Sunday.
Australian Kisnorbo was only promoted from assistant to interim manager of Yokohama F. Marinos last week following the sacking of Steve Holland after a disastrous start to the J.League left the team at the bottom of the table.
Jhon Duran, signed for over $100 million ($A156m) from Aston Villa in January, opened the scoring for Al-Nassr from close range.
Four minutes later, Sadio Mane doubled the lead, the former Liverpool forward firing home a fierce low shot from the left of the area.
There was still time before the break for Ronaldo to give Al-Nassr, looking for a first ever continental title, one foot in the last four. Goalkeeper Park Il-kyu spilled a shot from Marcelo Brozovic and Ronaldo, from close range, was on hand to score his 33rd goal of the season in all competitions.
Duran scored his second and Al-Nassr's fourth four minutes after the break, and Anderson Lopes grabbed a consolation for the five-time Japanese champions.
Al-Nassr's Saudi Pro League rivals Al-Ahli defeated Buriram United of Thailand 3-0.
The damage was done early. After just four minutes, former Manchester City star Riyad Mahrez scored with a low shot from the right side of the area after Buriram failed to clear. Two minutes later, Brazilian winger Galeno made it 2-0 and Roberto Firmino finished off.
Al-Ahli, two-time finalists, will take on Al-Hilal, the four-time champions, in an all-Saudi semi-final on Tuesday.
On Friday, Al-Hilal thrashed Gwangju 7-0 with all seven coming from different scorers.
After Al-Hilal's relatively poor run of form domestically, coach Jorge Jesus was delighted with the result and performance. "We've been under pressure in the Saudi Pro League, and the players have shown great focus despite that," Jesus said.
"Without commitment, we couldn't have achieved this. I believe we're on the right path, creating a good atmosphere for everyone involved — players and staff."
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