give the German set point at 6-4.
Zverev then struck a 130 miles per hour serve down the tee which Isner returned crosscourt wide from the backhand side.
In set two, Isner broke serve at four games all to lead 5-4.
Then serving at deuce, Isner struck an inside out forehand down the line winner to set up set point.
Isner struck a 143 miles per hour serve out wide which Zverev netted with a crosscourt backhand return to level the match at one set all.
The 32 year old American broke the 20 year old Zverev’s serve once again in the final set while never dropping his own serve to reach 5-4.
Isner served his 18th ace of the day to finish the match.
Following his Miami Open title, the American entered the ATP Tour Rankings’ top ten at number nine on Monday.
The six feet ten inches tall Isner’s best grand slam result to date is his 2011 US Open quarterfinal finish.
Known for his powerful serve, Isner holds the record for hitting the most aces ever in a single tennis match at 113.