WATCH | Australian Open: Fourth seed Alexander Zverev suffers shock defeat against Hyeon Chung

Relentless South Korean Hyeon Chung ground fourth seed Alexander Zverev into submission in a ferocious battle of young guns to reach the fourth round of the Australian Open on Saturday.

German wunderkind Zverev, tipped as a title contender, led by two sets to one but 58th-ranked Chung was unflappable and roared back to win 5-7 7-6(3) 2-6 6-3 6-0.

It all proved too much for 20-year-old Zverev, who began to unravel in the fourth set, complaining bitterly to the umpire that the lights should be switched on despite it being only 6 pm in overcast Melbourne.

"I can't see anything," the German told the official. The lights were duly switched on but once the bespectacled Chung took the fourth set, there only looked to be one winner.

Zverev, who is yet advance past the last 16 at a grand slam, double-faulted twice to gift Chung a break at the start of the fifth and when he dropped serve again two games later he demolished his racket, earning a warning.

The end came quickly as Zverev capitulated, netting a backhand to hand Chung victory as he became only the third South Korean to reach the fourth round of a grand slam.

"It was a really tough match, I was just trying to play 100 percent out there," Chung, a year older than Zverev, said on court. He will play either six-times champion Novak Djokovic or Albert Ramos-Vinolas in the next round.

Here are highlights

Can you all handle another battle??#NextGenATP stars Hyeon Chung takes on Alex Zverev in what we are sure will a fun contest...#AusOpen pic.twitter.com/c8EmDUfoH7

— #AusOpen (@AustralianOpen) January 20, 2018

Alexander #Zverev takes the first set!#AusOpen pic.twitter.com/tgwiYOnjaD

— #AusOpen (@AustralianOpen) January 20, 2018

Shot #AusOpen pic.twitter.com/MEEjcJxDHG

— #AusOpen (@AustralianOpen) January 20, 2018

How's that for precision... #AusOpen pic.twitter.com/O97uQyIvcB

— #AusOpen (@AustralianOpen) January 20, 2018

All square!

Hyeon #Chung takes the second set against Alexander #Zverev 7-6.#AusOpen pic.twitter.com/yj0n5sJxPN

— #AusOpen (@AustralianOpen) January 20, 2018

#AusOpen pic.twitter.com/GjWL827MYt

— #AusOpen (@AustralianOpen) January 20, 2018

Zverev saves two break points to hold serve, 2-1.#AusOpen pic.twitter.com/CSNzjngd6F

— #AusOpen (@AustralianOpen) January 20, 2018

Alexander #Zverev takes a  sets to  lead!#AusOpen pic.twitter.com/OcQie0PNgO

— #AusOpen (@AustralianOpen) January 20, 2018

New set. New shirt. No problem.

Hyeon Chung forces a decider vs Zverev 5-7 7-6(3) 2-6 6-3.#AusOpen pic.twitter.com/HSF9Loce0K

— #AusOpen (@AustralianOpen) January 20, 2018

It's all happening on @RodLaverArena!

Chung breaks to love in the first game of the fifth set against Zverev... #AusOpen pic.twitter.com/fjHOmfh8Sl

— #AusOpen (@AustralianOpen) January 20, 2018

Sascha - and his racquet - in a lot of strife...

Chung takes a double break at the start of the fifth set! #AusOpen pic.twitter.com/mGjLClOexN

— #AusOpen (@AustralianOpen) January 20, 2018

Making history.

Hyeon Chung becomes just the third Korean player to make the R16 at a Grand Slam, ousting No.4 seed Zverev 5-7 7-6(3) 2-6 6-3 6-0.#AusOpen pic.twitter.com/szU7TOljXZ

— #AusOpen (@AustralianOpen) January 20, 2018

Seeing is believing #AusOpen pic.twitter.com/163YbelpvY

— #AusOpen (@AustralianOpen) January 20, 2018

"It was a really tough game against Alex Zverev... I'm just trying to play 100% and that was the key today."

What a performance from Hyeon Chung - his first win against top five opposition! #AusOpen pic.twitter.com/01ADJcXoBu

— #AusOpen (@AustralianOpen) January 20, 2018

(Inputs from Reuters)