The world number two came good when it mattered in two tiebreaks on a hot and windy day for a 7-6 (7/1), 7-6 (7/0), 2-6, 6-1 victory over the 12th-seeded American.

Germany's Zverev also reached the semis in 2020, losing to Dominic Thiem, and again last year when he crashed to Daniil Medvedev in five sets after holding a 2-0 lead.

Now into the last four of a Grand Slam for the ninth time, the 27-year-old has never been able to go all the way and be crowned champion in a decade of trying.

He will need to beat 10-time Melbourne winner Novak Djokovic or Spanish third seed Carlos Alcaraz, who meet later, to reach Sunday's final and keep his goal alive.

"To be honest, I should have been down two sets to love," said Zverev, who is bidding to become the first German man to win a Slam since Boris Becker in 1996.

"I was not playing great, and I thought he was.

"But I somehow won the first set, somehow won the second.

"And the fourth set was definitely the best that I played and obviously extremely happy to be back in the semi-finals."

Zverev dropped his first set of the tournament in the fourth round to Ugo Humbert and repeated the feat against a persistent Paul.

The American, also 27, earned the first break of the match in game five, but Zverev repelled it to hold serve for 3-2 as the pair went blow for blow.

An unrelenting Paul kept pressing and a smart drop shot gave him three break points at 5-5. Zverev saved two but Paul converted the third when the German netted a backhand.

Undeterred, Zverev struck straight back to take it to a tiebreaker where he dominated as Paul became frustrated and fumed at the umpire over a disputed let call.

The American regrouped and a sizzling backhand winner saw him break then hold for a 3-0 lead in the second set.

This time it was Zverev's turn to lose his cool when the umpire called for a replay due to a feather floating in front of the German as he played a shot on break point.

"C'mon, that is unbelievable on break point," he shouted, before taking out his fury on Paul by breaking back to love.

It went to another tiebreak where Paul once again went missing.

But Paul broke early in set three and again for 5-3 as the Zverev serve misfired to take it to a fourth set, only for a loose forehand to then hand his opponent a 2-0 lead.

Zverev could sense victory and raced 5-0 clear as Paul wilted, sealing the win with an ace on his third match point.