"Just walking out for a Basel final was always my dream, already just playing on centre court was a thrill", Federer said.
The 32-year-old South African beat fifth-seeded Kei Nishikori 6-3 7-6 (3) to make sure he will feature in the London event, which runs from November 11-18.
The 28-year-old Copil came to Basel with career prize money - $1.67 million - significantly less than Federer earned just for winning the Australian Open in January. I know I can play at a high level and keep it up with the great players. He needed 44 minutes to claim the opening set but was brought back to level-pegging as Zverev won the second in a tiebreaker. "I was a bit unsure of my serve and his return is excellent", said Federer.
Federer hinted after his latest victory that he may not play at the Swiss Indoors in the future.
"I played quite good tennis, it was an wonderful week", he said.
Federer was given a stern test by world No 93 Marius Copil but still won 7-6 6-4.
His qualification means there are two places still up for grabs ahead of the Paris Masters, with Croatian Marin Cilic, Austrian Dominic Thiem, Nishikori and American John Isner still in the race.
Germany's Angela Merkel Says Will Step Down As Chancellor In 2021
Merkel's party managed an unimpressive win, narrowly salvaging a majority for its regional governing coalition with the Greens. Mrs Merkel's conservative CDU party now rules along with the centre-left Social Democratic Party (SDP).
Joe Salisbury and Neal Skupski beat America's Mike Bryan and France's Edouard Roger-Vasselin 7-6 (5) 6-3 in the doubles final in Vienna.
"It's been an unbelievable week for me so far", Copil said.
It was early trouble for the World No.3 when he fell 5-2 behind.
Just as Federer looked to be settling into form after almost 30 unforced errors in the opening set, more disruption ensued. After tamely surrendering the first set in 20 minutes, Medvedev found himself trailing 5-1 in the second but managed to fend off a match point and hold serve.
There were five breaks of serve in the second set with three of those claimed by Simon as the Frenchman rallied to even out the scoreboard.
Federer broke back in the sixth game after a poor drop shot from Copil, with both players serving well after that to reach a tie break. But he finally lost his nerve in the 12th game when two unforced errors in a row handed Federer the match.