Im playing a HC P8 zealer in Act 5 normal and zeal + holy freeze is like a hot knife through butter. I got lucky and found hotspurs in Act 1 so that helped too.

Iso act 1 hell update

Is that when zealer stops working well

This

elemental zealers smash through norm and nm very easily but begin to struggle in hell

Try holy shock at that lvl, just put in zeal for 5 hits and rest in aura and synergy.
2.2k dmg, and you kill small things with 2 procs of aura.
But then hell comes ^^

Then you are dependant on physical damage only
Your charms and gear will be bad

So in hell I will need to respec to zeal fanat and get a good weapon and some safety gear? I am going to look for a butchers pupil that I can upgrade, and probably try to make a nice eth Oath after that

What a convenient thing to drop right before walking into the throne room

Then you'll have the problem of physical immunes, at least they are less frequent than cold/light/fire immunity.