Please note this video is unofficial video of Sega, Creative assembly or Feral Interactive.

Hi, you would able to pay attention that when attacking Sacred band, I use both a normal attack (charge) and an alt attack after contact. Since this method takes time, even if you successfully defeat three Sacred band, you will only have peltasts left on your side, but it is manageable if your losses are not too large. Lure their hoplite one by one with decoys and hit them from behind. You have no choice but to repeat this. If you are not confident, you can be deep in the mountains or anywhere else, run far away. It will be easier if you let enemy units be exhausted and let your cavs recover from their fatigue. (However, only the enemy general should be defeated early.)

This battle on veryhard difficulty is extremely too difficult. Don't blame yourself if you don't succeed. It all depends on whether you can defeat the three sacred squads without getting too much damage. You are free to use wedge formation or not.
In this video, the second Sacred band suffered friendly fire from an allied Javelin, which might be the cause of the rout, and I was lucky. Anyway, if the Sacred band does not move as expected or it takes too long to destroy the three units, it is better to start over.