I visited Tchogha Zanbil (as well as the other nearby WHS) on a long day trip from Ahwaz, between two overnight bus trips. This is not a recommended way to see these sites, as you can find yourself at the whims of an unpleasant driver who decides to double the price of the trip halfway through.
While I showed this driver (the only one at the station willing to take the trip) my map showing a route of Ahwaz-Susa-Tchoga Zanbil-Shushtar-Ahwaz, he nevertheless insisted on going to the ziggurat first, expressly denying the existence of a clearly-marked road linking them east-west. This caused pointless doubling back, which he repeatedly passive-aggressively blamed on me.
Approaching the ziggurat, I was amused by signs prohibiting the use of firearms. This instruction seemed a lot less comical when I arrived at the site to find nobody else there, with what could only be the sound of automatic gunfire in the middle distance. Combined with what seemed to be angry yelling, the eeriness of this experience soured my visit, as I didn't feel super comfortable being there in such a situation. I'm sure in reality it was perfectly fine, and once back in the car I felt a bit silly for worrying, but I nevertheless couldn't shake an uncomfortable feeling. As such, I didn't really do much more than a quick circumnavigation of the ruins, which is a shame.