What Rage activates

Divine Fury adds damage while raging, Fanatical Focus can rescue one failed save during each Rage, and Rage Beyond Death eventually lets the Zealot remain conscious at 0 hit points as long as the Rage continues.

What remains useful outside Rage

Warrior of the Gods remains relevant whenever resurrection magic is needed, and Zealous Presence can empower allies without being the same kind of constant Rage rider as Divine Fury or Rage Beyond Death.

The normal Rage restrictions still matter

Divine Fury, Fanatical Focus, and Rage Beyond Death make Rage especially valuable to a Zealot, but the normal 2014 spellcasting and concentration restrictions still apply. Multiclass magic therefore has to be planned around Rage rather than assumed to function through it.

Why Rage duration matters

Rage ending is life-or-death at 14th level. A Zealot that has accumulated fatal death-save failures through Rage Beyond Death must be above 0 hit points before the Rage ends or the delayed death takes effect.