Federer may be in control of the match but he still can't get his challenges right. He called for the Hawk-Eye on a Zverev lob which just clipped the line.
Zverev isn't doing much wrong in this match so far but he's been undone by Federer's brilliance. He's only committed 3 unforced errors in the match but finds himself trailing by two-sets-to-love.
Easy holds from both players to start the third set. Federer has so far hit 39 winners and just 10 unforced errors. He's also sent down 5 aces.
Into the third set we go!
Mischa Zverev, after beating Andy Murray, is facing a completely different match tactically. The 29-year-old's approaches to the net have been dealt very effectively by his Swiss opponent. Federer has volleyed, chipped and smashed at the net to take a convincing lead in this quarter-final.
Federer has one foot in the semi-finals, with Stan Wawrinka waiting to face the winner of this match.
Great to see so many court-level camera angles used in this Federer-Zverev match. Much better way to grasp the volley/passing shot duel
The four-time Australian Open champion needed 36 minutes to wrap up a more evenly contested second set, 7-5.
Federer starts with another forehand winner after Zverev dropped the ball short on his return.
The Swiss brings up three set point sbut the German saves the first two. On the third point, he sends his return long.
Federer waited for his opportunity and as soon as he saw a opening, he hit a one-handed pass beyond Zverev's reach. Three break points for the Swiss and he didn't need to be asked twice. He pounces on the very first one and breaks for 6-5. Federer will now serve for a two-sets-to-love lead.
Important 10 minutes coming up in this set as Zverev now serves at 5-5. Federer will be looking to break to end this set soon.
Federer living dangerously as he goes down 15-30 on his serve. With a composed inside-out forehand into the open court he makes it 30-all.
Two holds, but Zverev right now is the player with momentum. It's 5-4 Zverev on serve: Mischa is taking Fed's time away, asking questions.
Zverev hits a perfect ace down the tee and holds to love to edge ahead 5-4. Federer will now com out and serve to stay alive in the second set. After the lopsided opening set, this match has now turned into an interesting tussle. A few more errors have creeped into the Swiss player's game while Zverev has only grown in confidence.
At 40-30, Federer hits a glorious backhand down the line and Zverev sends his return long. It's 4-4 on serve.
Here's a look at the stats from this match so far. Federer with 22 winners as compared to Zverev's six.
A game of cat and mouse going on at the Rod Laver Arena, with both players trying to outdo each other at the net. When one approaches, the other attempts to pass him. Intriguing contest building up in the second set.
Zverev with an incredible cross-court passing shot and it's 30-15 on Federer's serve.
The next point sees a long rally which ends with Federer dumping a backhand slice into the net. 30-30.
Federer immediately brings up two break points of his own on the very next game. And he ensures Zverev can't consolidate. The second set is back on serve, 2-3.
Three break points for Zverev and he converts his very first one! Nice turnaround in the second set as the German leads 3-1.
Zverev is playing much better in the second set and has been able to hold his own at the net against Federer. It's on serve at 2-1.
Zverev holds to start the second set. He will be looking to do better in this one after getting completely blown off the court in the opener.
First set to Federer!
19 minutes, 18 winners and Roger Federer wins the first set 6-1 over Mischa Zverev in their quarter-final.
Federer hits a glorious forehand down the line to bring up set points!
He sends his next shot long and it's back to deuce.
Federer then fires an ace to bring up set point number 2.
Zverev finally gets on the board 15 minutes into the match. Federer will now serve for the first set at 5-1.
Consolidation at love, as Federer leads with a double break at 5-0. He is striking the ball so cleanly so far into the match and passing Zverev on every occasion.
Unlike Murray in his last match, Federer has come prepared with a gameplan to neutralise Zverev's net game. He's passing him on every opportunity and lobbed him on the last point to bring up three more break points.
Federer converts to make it 4-0. All going the 17-time slam champion's way so far!
The last time these two players met, Federer defeated Zverev 6-0, 6-0. Here's a video to jog your memory.
Preview: Seeing world number 50 Mischa Zverev and wildcard Denis Istomin upset the top two players in the world at Melbourne Park shows more players believe they can take shake up the established order and that can only be good for tennis, says Roger Federer.
Zverev's win over world number one Andy Murray on Sunday came on the heels of Istomin's second round victory over six-times champion Novak Djokovic, results which not only surprised Federer but saw the odds of him winning the title shortened.
Roger Federer makes a backhand return during a practice session at the Australian Open. AP
"I never thought that Mischa Zverev and Denis Istomin would beat those two big guys," said 17-times grand slam champion Federer, who will play Zverev on Rod Laver Arena on Tuesday.
"I guess it's good for tennis that a lot of guys believe stronger now that the top guys are beatable, are vulnerable, especially on a faster court.
"But two huge surprises. No doubt about that."
Federer added that he would practice against a left-hander before the clash with Zverev, who charged Murray at the net and put the Scot off his rhythm from the baseline in their fourth-round encounter.
"Obviously he's on a high right now. He's feeling great," the Swiss said of Zverev. "Probably feels the best he's ever felt on a tennis court.
"It's going to be tough and different and tricky."
Things will not get any easier for Federer should he get past the 29-year-old German, with compatriot Stan Wawrinka or Jo-Wilfried Tsonga waiting for him in the last four.
Tsonga said he was taking it one match at a time.
"It's going to be a tough match," he said of Wawrinka. "I know he's playing really good.
"If I win, another opponent, and if I win, another one, so ... the most important thing for me is to be focused on the next opponent."
In the women's quarters, Venus Williams has the chance to send a positive message to all the veterans at the tournament when the 36-year-old takes on Russia's Anastasia Pavlyuchenkova, 11 years her junior, in the first match on Rod Laver Arena.
Williams could meet her younger sister Serena in a ninth grand slam final if they both get through the draw but she is refusing to think about that scenario just yet.
She would first have to get past Coco Vandeweghe or French Open champion Garbine Muguruza in the last four.
"She's a tricky player," Muguruza said of the 25-year-old Vandeweghe. "She has a lot of power, full shots, serve, everything. She can play very well."
Order of play on main courts at the Australian Open on Tuesday (x denotes seeding):
Rod Laver Arena:
11:00am (0000 GMT)
Venus Williams (USA x13) v Anastasia Pavlyuchenkova (RUS x24)
Not before 1:00pm
Coco Vandeweghe (USA) vs Garbine Muguruza (ESP x7)
Stan Wawrinka (SUI x4) v Jo-Wilfried Tsonga (FRA x12)