Lewandowski has again been prolific this season, scoring 20 league goals to top the Bundesliga scoring charts and put Bayern on track for a sixth straight title.
The Poland international has been strongly linked with a move to Madrid at the end of the season, with the La Liga giants reportedly ready to offload Karim Benzema after a poor campaign.
Lewandowski has shrugged off rumours about his future, but the appointment of Israeli agent Zahavi will spark further speculation he is considering leaving Bayern.
"I am glad that Robert decided to cooperate with me," Zahavi told Polish newspaper Przeglad Sportowy.
"I will do everything to work well in his name.
"He is a great footballer. He is the best striker in the world. Therefore, it is not surprising that I have signals about the interest of his person in all major clubs."
Zahavi would not be drawn on the reported interest from Madrid in Lewandowski, however.
"Will Robert go to Real Madrid?" Lewandowski's new agent added.
"We'll see. Now it's time for me to do my job."
Zahavi reportedly played a role in Neymar's world-record €222 million move from Barcelona to Paris Saint-Germain in August, while reports in France have also indicated Zahavi has links with PSG sporting director Antero Henrique.
Lewandowski hit a brace as Bayern demolished 10-man Besiktas 5-0 in the first leg of their last-16 Champions League tie on Tuesday, taking his tally for the season to 29 in all competitions for the Bundesliga champions.