Slowly reduce the Timurids or whoever controls the Eastern Iranian area. Dont attack in the West and try to build a long term alliance with either the Mamluks or Ottomans. It is possible to see the achievements sorted by the percentage of users that managed to complete each achievement by going to the game' Achievements have no in-game effects the achievement just pops up in-game and then added to the player's Steam profile.
Home Eu4 Timurids achievements Achievements - Europa Universalis 4 Wik