All that is required for this achievement is to ensure you have Zhang in your squad when launching the final mission on the temple ship. Once the Skyranger lands and you have control of your squad, the achievement will unlock.
NOTE: This is missable because if you don’t have Zhang included in your squad, you will be forced to either load an earlier save or restart the entire game. Also be sure that Zhang doesn't die if you take him on missions prior to the final mission. If he does, you will be forced to reload a previous save or restart from the beginning.