Cooper and Sexton traded penalties during a scrappy, penalty-marred first quarter. Winger Nick Cummins put the visitors ahead for good in the 17th minute at the end of a series of sharp passes that wrong-footed Brian O'Driscoll and Tommy Bowe.
Cooper drew in O'Driscoll, faked a long pass to Cummins that committed Bowe, and dumped it off short to Stephen Moore. The hooker burst through a gap and fired a one-handed pass to Cummins, who sprinted untouched to the posts after cutting inside as two confused defenders covered the corner.
Australia attacked that same vulnerable spot seven minutes later. Scott Fardy burst down the sideline and cut open the defense with a back-handed offload to Michael Hooper at his shoulder. It was Hooper's first try for Australia.
Ireland trailed only 15-12 at the half thanks to four penalties from Sexton, who was injured in the final seconds of first-half play. He was replaced by Ian Madigan, who hit his only penalty attempt.
"Our defending was naive at times," Ireland coach Joe Schmidt said. "I felt just before halftime we'd fought our way back into the game. But losing Jonny didn't help."
The visitors overwhelmed Ireland after the break with an increasingly muscular display that left O'Driscoll in a heavy head dressing from a cut over his right eye, fullback Rob Kearney writhing in pain with bruised ribs, and Peter O'Mahony lucky to avoid injury after being dumped on his head.
Kuridrani picked up O'Mahony's legs and dropped him head first. He was red-carded for a dangerous tackle and faces likely suspension.
Australia nearly scored a try immediately after the restart, but Cummins' broken-tackle burst past Bowe was disallowed because he lost control of the ball before touching down.
The Wallabies didn't have to wait long, though. Cooper received a long pass from the ensuing five-meter scrum, faked a pass wide and cut between Madigan and center Luke Marshall.
Hooper scored his second try at the back of a ferocious maul that marched 10 meters across the Irish tryline. The score put an exclamation point on an Australian performance that few expected against traditionally physical, hard-tackling Ireland.
"Obviously I'm pleased to get my first test tries. But it's extremely good for the team to get back-to-back wins for the first time this year," said Hooper, referring to Australia's 50-20 defeat of Italy last week. Australia has lost eight of its 13 matches this year.
McKenzie said Australia was ready for Ireland's reliance on choke tackles and strength in the maul with locks Paul O'Connell and 6-foot-11 Devin Toner.
"We worked hard to nullify the strengths of their game, and we still wanted to express ourselves and demonstrate how we've been developing. I think we got the two right," he said.
The Irish twice were denied consolation tries in the final minutes. New Zealand referee Chris Pollack called back Conor Murray's try because of a quick tap. Then replacement hooker Sean Cronin was denied his first try for Ireland because a video review spotted a knock-on in the build-up ruck.
The battered Irish face powerful New Zealand next weekend. Schmidt said he didn't think Sexton would play and conceded that the prospect of beating the All Blacks was "a very tough ask."
Australia concludes its test campaign this month with matches against Scotland and Wales.
- AP
