Birthday boy Zverev roars back to form with Munich win
The top-seeded Zverev, appearing in his first final since losing to Jannik Sinner in the Australian Open title decider in January, had little trouble dealing with Shelton, ranked 15 in the world.
For Zverev it was the third time he had won in Munich -- equalling compatriot Philipp Kohlschreiber's record -- and his 24th ATP title overall.
Unlike in his quarter-final win over the Netherlands' Tallon Griekspoor, where Zverev needed to come from a set down to win, the German was in control from the outset against the 22-year-old second-seeded American.
Zverev forced Shelton into several mistakes, before converting his first match point after just 71 minutes.
"It's been a difficult few months," Zverev said, while thanking the home fans: "without you, I would already be out.
"On Friday, I was already almost out, but now I'm standing here with the trophy."
Sunday's match was the first time the top two seeds met in the Munich showpiece since 2010.
Shelton congratulated Zverev on the win in his "home tournament", adding "congrats to your team, you guys are doing great work and are playing really well.
"I would have liked to have said this is a birthday present, but I had no clue it was your birthday.
"I feel blessed to play in front of you guys on Easter Sunday, it's really special for me."
Zverev returned the praise, saying Shelton was "becoming one of the most dangerous players on every surface and it's great to see."
Shelton was bidding to become the first American to win a final on clay above ATP 500 level since Andre Agassi in 2002.
Zverev's win on Sunday represents a welcome return to form for him.
After losing to Sinner in Melbourne, Zverev failed to make it past the quarters at six successive tournaments, before coming to Munich.
The German, most comfortable on clay, repeatedly said he was not concerned about his form and was focused on the French Open, which begins in late May.
Winners of the tournament pocket almost half a million euros ($570 million), along with a luxury car from the sponsors and a pair of lederhosen, traditional Bavarian leather pants.