The Hammers have been linked with an array of strikers in recent weeks, and co-chairman David Sullivan admitted that he would "love" to bring Ibrahimovic to the club.
The Sweden international himself revealed that he has received offers from the Premier League ahead of his Paris Saint-Germain contract expiring at the end of the season, but Bilic doubts whether West Ham will be able to pull off the deal.
"I don't know. Nothing is unrealistic, but I said my opinion. I can't see Ibrahimovic playing for West Ham," he told reporters.
West Ham currently sit fifth in the Premier League table, just one point short of the Champions League places.