Fully upgraded scythe chariots mean nothing against elephants, postapocalypic. A total waste of resources. Against Hittite players the Persians don't even need to build towers: walls to keep out the scythes and archers are enough. Hittite catapults take much more gold than elephants do, and they're not that good against Persians.
Since there's nothing to stop Persians from building catapults against Hittite players, I seldom really fear phalanxes and heavy horse archers(not that I believe they exist: I have _never_ seen anyone build one in a RM they had not already won).
My experience of Hittites in iron against Persia is that they are forced into an almost completely defensive posture. They can certainly win a game that goes long enough, but it takes everything they have in early iron to just not die. I concede that if untouched they have a far better economy than the Persians do, but they're going to be defending, running, defending, replacing buildings and farms, losing a fishing fleet, and replacing any villagers elephants get near for about 10 minutes in iron. Oh, and researching to get any decent iron units. Persians get to iron and research at most four technologies that require food - catapult, trireme, cavalry chainmail, and engineering(eventually fortification, the two shields, and armored elephant, as well, but those can certainly wait).
None of the Persian technologies is essential, except maybe catapult. Hittites must research far more to compete with the super elephants and priests. Persians have, then, a big edge in early iron productionn on the overworked Hittite peasants. It isn't practical to pump Hittie elephants out against a Persian player, either, given the difference in priest quality and the difficulty of catching the Persian elephants in the first place. Archers die to Persian catapults(or, if you're inclined that way, elephant archers(which suck)..or camels, if the Persians have any left over). Chariots will keep the priests in check...for as long as they're around against elephants. Most Hittite players don't build them, and I don't, when I play Hittie, until quite late in iron.
Phalanxes are fine against elephants, as long as no one has catapults firing into the battle. This is very seldom the case, and when it is, the Persians can run away.
Economic bonuses aren't worth much when you don't control enough of the map.
I honestly don't believe that any civilization that depends on chariots or chariot archers to do the job can compete with the Persians, postapokalypic, and that's why I believe that every civilization against Persians is gold dependant. Persians are very beatable - much more so than Hittites are - but you do it with academy, helepoli, or priests, not with catapults or archers or elephants.