I had formed Persia and got this achievement a while ago. But I won’t use “This is Persia” as title because it is very misleading. I wanted it, but I am not even half way there yet.
After I formed Persia with Tarbarestan, my old rival Timurid was still in nomad technology with unreformed government. Also, I received claims from it. In the same time, Timurid was still unstable as F. Although it still has some horde allies, they are all behind in technology. So it is definately a good idea to go attack them!
In the same time, QQ, Armenia, Oman and Shammar seem like to a good targets for expansion. And in fact, they are! It just that -2 local missionary strength makes it hard to convert.
Slide show below is the progress of how I expanded my Persian empire, and soon start rivaling the Muscovy and Ottoman. It is better than uploading 24 images, let see how this turn out