Hardik did not bowl for the defending champions in their first two fixtures.
Pandya, who underwent a back surgery in London last November, did not bowl for the defending champions in their first two fixtures.
"We are all expecting him (Hardik) to bowl and he is someone who really changes that balance of any side when he is bowling and he understands that," Zaheer said when asked about Hardik's bowling, as quoted by PTI.
"But we have to listen to his body and that is something the conversation which we have been having in consultation with the physios.
"We are looking forward for him to bowl, he is very keen and really wanting to bowl, we just have to wait and be patient and listen to his body. At the end of the day for any bowler injuries play a huge role."
Hardik scored 14 and 18 in the first two matches against Chennai Super Kings (CSK) and Kolkata Knight Riders (KKR) respectively.
"We are happy that he is there as a batter and with full fitness contributing and that is the exciting part and hopefully you will see bowl soon," Zaheer stated.
Mumbai Indians bounced back brilliantly with a thumping 49-run victory over KKR after losing the tournament opener by five wickets versus CSK.
Zaheer is hoping the team's spinners to play a crucial role in the upcoming games.
"As a bowling unit, we have been doing a fantastic job. In this format you have seen batters putting pressure on bowlers and you have to stay on top of the game, so that is something which you have seen from our spinners in the last game and that is something you will see going forward," the former India pacer said.
"Rahul Chahar is a fantastic leg-spinner and has had a brilliant last season and he is looking in good form. As far as matches are concerned, it is a matter of time, things fall in place."
(With PTI inputs)