Currently only the NE version of Zimbra is the only one to have 2FA, the OSS version is left out in the cold (as usual, IMO).
If you would like to help get 2FA implemented in the OSS version as well then please consider a donation to the following crowd funding project: https://fundrazr.com/51S949?ref=ab_f6Ty ... N5VLcLlCOP
Any donation, however small, will help get this feature off the ground and continue it's development so don't be shy and add your name to this project.