Andy Murray continued his eventful start to the season with a notable win over Germany's Alexander Zverev to put him into the Qatar Open quarter-finals.

"I managed to stay strong, keep fighting and get the break at the end," said the former world number one.

French qualifier Alexandre Muller, ranked 170th, awaits Murray next.

"I would like to win the matches quicker but Alex is a top player and a great competitor, who always fights until the end," added Scot Murray after upsetting fourth seed Zverev.

"In the third set I was hanging on and he was making better chances."

It was another gutsy win from Murray in a year where all of his four wins have come in dramatic circumstances.

At the Australian Open, he survived a match point to beat Italian 13th seed Matteo Berrettini in the first round and then fought back from two-sets down to win at 4am against Thanasi Kokkinakis in his next match.

On Monday, he saved three match points before winning a final-set tie-break to beat Italy's Lorenzo Sonego in Doha.

Elsewhere, at the Rio Open in Brazil, British number one Cameron Norrie reached the quarter-finals with a 7-5 7-5 win against Brazil's Thiago Monteiro.

In a two-and-a-half-hour epic, second seed Norrie created 21 break points, of which 16 were saved, and clinched a last-eight tie with Bolivia's Hugo Dellien on his sixth match point.

More Murray magic

Against 25-year-old Zverev, Murray eventually came out on top in an intriguing contest between two players who have both suffered serious injuries, and which acted as a gauge of their respective progress.

Three-time Grand Slam champion Murray might not be blessed with the physical capabilities of his peak after the hip surgery which he thought would end his career.

But, as we saw in Melbourne, the talent is still there to make the very best opponents solve the problems he creates and the desire to beat them remains stronger than ever.

Murray twice fell a break behind in a competitive first set, but continued to ask serious questions of the 2020 US Open runner-up with his clever returning.

Zverev, who snapped ankle ligaments in a French Open semi-final against Rafael Nadal last year, was unable to serve out at 5-4 and the opener swung the way of Murray in a tight tie-break.

The one-sided nature of the second set was a stark contrast.

Murray's physical levels dipped and his plummeting service percentage enabled Zverev to break twice and the world number 16 appeared to hold the momentum in the decider.

Murray, ranked 70th, had to scrap to hold serve early on as Zverev dominated his service games.

But, like we have seen him do so many times, Murray survived the pressure and held serve when two points from defeat at 5-4.

The quality of a momentum-changing drop-shot helped Murray break for 6-5 and he served out victory to stop Zverev winning one of the sternest tests he has faced in his comeback.

What happened elsewhere?

British number six Liam Broady lost 6-4 6-3 to former world number one Daniil Medvedev, seeded third, in his second-round match.

Top seed Andrey Rublev, another Russian player, saved three match points before eventually beating Dutchman Tallon Griekspoor in a 1-6 6-1 7-6 (8-6) success.

On the other side of the draw, Canadian second seed Felix Auger-Aliassime also fought back to win 4-6 6-1 6-4 against Australia's Jason Kubler.

At the WTA event in Dubai, Poland's world number one Iga Swiatek continued her dominant form with a 6-1 6-0 win over Russia's Liudmila Samsonova.

Swiatek, 21, later received a walkover into the semi-finals after next opponent Karolina Pliskova withdrew through illness.

Belarusian world number two Aryna Sabalenka, who won her maiden major title at the Australian Open, earned a 13th win in 13 matches this year by beating defending champion Jelena Ostapenko 2-6 6-1 6-1. She will face the Czech Republic's Barbora Krejcikova in the last eight on Thursday.