I was studying Fotona website, I noticed they have developed two FCS system for MBT's, EFCS-3 for T-55 and T-62 and TFCS-3 for T-72 and M-84.
So I think most likely standard EFCS-3 (that Iran used it to upgrade T-55/54 to T-72z and later reverse engineered and produced with the name of KAT-72) can't be used on T-72, M-60, Chiftain and Zulfiqar, and It should be modified , So maybe one of the reason Iran hasn't used KAT-72 on T-72's or Zulfiqar till now is that they have developed different modified EFCS-3 for different MBT's and there are different types of KAT-72 for different MBT's And development of KAT-72 for T-72 and Zulfiqar has been finished recently.
I read on modlex that they are installing KAT-72 on numbers of T-72's now, after successful operational tests of this system. they have planned to equip T-72's with this system.