Zakani made the announcement in a post on his X account on Thursday a day before the presidential elections.
He has asked other candidates either Mohammad Bagheri Ghalibaf or Saeid Jalili to leave the course to secure victory for the Revolutionary Front.
Zakani became the second contender to quit the contest after Amir-Hossein Ghazizadeh Hashemi announced his withdrawal in a statement on Wednesday.
The candidates remaining in the race are Saeed Jalili, a former lead nuclear negotiator, Mohammad Baqer Qalibaf, Iranian Parliament speaker, Mostafa Pourmohammadi, former interior minister, and Masoud Pezeshkian, former health minister.
MNA