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NOW: Alexander Zverev beats Carlos Alcaraz 6-1 6-3 6-7 (2-7) 6-4 in men's quarter-finals
German will play Daniil Medvedev, who beat Hubert Hurkacz 7-6 (7-6) 2-6 6-3 5-7 6-4
Qualifier Dayana Yastremska beats Linda Noskova in straight sets to reach first major semi-final
Zheng Qinwen beats Anna Kalinskaya 6-7 (4-7) 6-3 6-1 to reach women's singles semi-finals
Britain's Neal Skupski and American partner Desirae Krawczyk reach mixed doubles final
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That Zverev first set puts Norrie’s narrow loss to him in the round of 16 into context. Zverev played brilliantly against Cam, too.
Anon
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Zverev 6-1 1-1 Alcaraz*
Alcaraz tries a drop shot, but Zverev is alive to it and is able to quickly pounce and comfortably put away a winner.
Zverev then attempts a drop shot of his own, but again it is read and punished, although that is the only point the sixth seed loses in a hold to 15.
*Zverev 6-1 0-1 Alcaraz
Gigi Salmon
BBC Sport tennis commentator on BBC Radio 5 Sports Extra and BBC Sounds
Image source, Getty ImagesWhen Alexander Zverev is at his best, he's one of the best in the world with that serve and with that backhand.
It all clicked in that first set. It was frightening.
*Zverev 6-1 0-1 Alcaraz
How will Alcaraz respond? A hold to 15 in the opening game of the second set from him is a strong indicator that this match still has a lot left in it and a long way from being over.
Zverev 6-1 0-0 Alcaraz*
Jonathan Jurejko
BBC Sport in Melbourne
There is a sense of shock around Rod Laver Arena.
"I did not expect that," says a fella sat behind.
When Zverev thumps down an ace to fnish the set, a Spanish journalist mutters: "Mamma mia."
Zverev has rocked Alcaraz - and everyone else - with that devastating opening set.
Zverev 6-1 0-0 Alcaraz*
BBC Radio 5 Sports Extra
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Zverev 6-1 0-0 Alcaraz*
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
The serve is operating well for Alexander Zverev. This is just the start he would've been hoping for.
Zverev 6-1 Alcaraz
Alexander Zverev with a stunning 29-minute first set, taking it 6-1 and ending it with an ace.
Carlos Alcaraz knew it was an ace as soon as Zverev hit it and was quickly walking off.
The sixth seed takes the lead with the second seed having a lot of work to do.
*Zverev 5-1 Alcaraz
Russell Fuller
Tennis correspondent on BBC Radio 5 Sports Extra and BBC Sounds
Carlos Alcaraz, in an endearing way, looks quite puzzled. He's not got the solutions at the moment.
Alexander Zverev is playing a breath-taking first set.
*Zverev 5-1 Alcaraz
A one-handed backhand while sprinting looks spectacular from Alcaraz but he has just pushed it wide.
He then runs around to get it on to the forehand and that flies long. Zverev at 30-0 and two points from the first set.
*Zverev 5-1 Alcaraz
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
Since Carlos Alcaraz burst on to the scene, winning the US Open and Wimbledon titles, he's been able to adapt. He can be explosive and doesn't mind going to net and finish the point up there.
*Zverev 5-1 Alcaraz
Image source, Getty ImagesAn error on the forehand side from Alcaraz as he nets and Zverev gets the double break.
Can he finish the first part of the job off? He's serving for the opening set.
Zverev 4-1 Alcaraz*
A great backhand winner from Zverev is followed by a lovely low forehand blaster down the line to give him a break point.
He'll be serving for the set if he gets it.
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Sobi: Age is just a number, and one's strength and capabilities can transcend any numerical value. Keep embracing the mindset of strength and vitality.
Falcon: Experience matters a lot. Age is just a number.
Zverev 4-1 Alcaraz*
Alcaraz is having to battle hard in each of his service games, also coming close to running out of time when serving.
Zverev has time to power a forehand, but an unforced error sees him slap it into the net when you would've expected him to pile on the pressure. Still, he gets to deuce and again is looking for another break of serve.
Zverev 4-1 Alcaraz*
Image source, Getty ImagesZverev is serving superbly and an ace helps a love hold and after only 17 minutes of action he has raced into a 4-1 lead, needing only two more games to take the opening set.
A start not many would have predicted.
*Zverev 3-1 Alcaraz
Having given Zverev a three-game headstart, Alcaraz is up and running with his first game of the match. He had to work hard for it to after being taken to deuce but managed to avoid falling 4-0 behind.
Zverev 3-0 Alcaraz*
Jonathan Jurejko
BBC Sport in Melbourne
At the changeover there was a hum of noise, a murmur of mild shock.
Sounds like very few people inside Rod Laver Arena expected Alexander Zverev to race into a 3-0 lead.
Zverev 3-0 Alcaraz*
Image source, Getty ImagesA lovely cushioned volleyed drop shot from Alcaraz is his stand-out shot of his match so far, but a blistering forehand down the line from Zverev has taken us to deuce, with Zverev aiming for 4-0 and a double break.
Zverev 3-0 Alcaraz*
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
Image source, Getty ImagesYou'd have to describe it as an edgy, nervy start from Carlos Alcaraz. That's a phenomenal start from Alexander Zverev.