Zombies and fire giants

[brian14]

1. Do fire giants have vulnerability to cold?

2. Zombies are resistant to blunt weapons. My main melee set is holy mace of pure good and holy burst light hammer of pure good, so zombies take +3d6 (or more) with each hit. Still, CR 13 super-zombies in Orchard take an awful long to kill. Would I be better off using edged weapons? I tried the best (for this purpose) edged combination I have -- frost bastard sword and icy burst sickle, -- and they still take an awful long to kill.

My Improved Critical feat is on ranged, so it makes no difference in edged vs. blunt.