In my experience the best way to level a zealer is go 1pt holy fire until u get 1pt holy freeze, don't commit to anything before holy shock, then max that and play as a tesla until hell. lvl 20+ holy shock with zeal and a fast wep (steel is great here) just shits on everything until hell. A few points in Vengeance early on could be useful but if you're going for holy shock you're not really looking for physical anyway, I'd rather spend these points in resist lightning for synergy or holy shield for survivability.
I'm far from a d2 expert tho so maybe someone else on this lovely board has better ideas.
Btw have really been enjoying the java so ofc tracking this!