I am Lvl 31 when I defeated Zash (L32), one shot. Heres how I did it:
1) Tank specced, Dark Ward 100% uptime
2) Use Andronikos Revel
Start the fight, immediately run out of Zash's range (30m), stay out of range as much as possible and taunt when losing aggro. If she gets close, electrocute her and force speed away. While she is chasing you around, your companion is unloading on her
Your pirate companion is an excellent ranged dps and will bring down Zash's HP in no time. As soon as she is down to about 30%, charge in and give her a good spanking.
I use this same strategy for all boss fights. Works even better if the boss is a melee like Jedi Commander.
Enjoy