PARIS (Reuters) -Alexander Zverev has reached the highest level of tennis in many ways, but Grand Slam glory continues to elude him and the German world number three appears to have found a philosophical acceptance of his place in the sport's hierarchy.

Last year's runner-up cantered into the second round of the French Open with a dominant 6-3 6-3 6-4 victory over American Learner Tien on Tuesday, but refused to look further in the draw.

"This is who I am, unfortunately. I have up-and-downs. I'm not a Novak Djokovic, I'm not a Rafa Nadal who is going to win or make finals of every tournament," Zverev, who has lost three Grand Slam finals, told a press conference.

"My highs are very high, and I realised that, but my lows are lower than other players and other top guys. I have come to terms with that, as well. That's just how my tennis is. You know, that's maybe who I am, in a way.

"I'm just hoping that my highs will be higher than anyone else's the next two weeks."

The third seed broke once in each set to advance comfortably and set up a meeting with Jesper De Jong of the Netherlands.

"It was a good start to the tournament," said Zverev.

"I'm happy with the three-set win, usually it's more four or five sets in first matches. Hopefully, it will continue like this and it will be a fun two weeks here."

The fact that Tien, the world 67, had already beaten him, helped Zverev keep his feet on the ground throughout on court Suzanne Lenglen.

"He beat a lot of great opponents - (Daniil) Medvedev at the Australian Open and me in Acapulco," Zverev said.

"He is going climb up the rankings. Today it helped that I played him once before, maybe it helped that I lost also to him. I am happy with the performance all around."

(Reporting by Julien Pretot; Editing by Ed Osmond)