Despite only having 70% critical chance with [Blood Rush] that number will stack insanely high super quickly with the addition of [Drifting Contact]. Because when you Gild a Zaw you can choose a polarization this will only require one Forma but if you decide to use both Sacrificial critical mods you'll have to use 4 forma(plus your one free polarized slot) assuming you don't use a Umbral Forma(I don't recommend using one!).
If your preference is a Polearm simply replace the grip with Shtung and whatever Stance you prefer I just wanted to try this with [Cyclone Kraken], which I've heard is an amazing stance. If you do want to make a Polearm though I recommend a Status build just cause it will scale into endgame content better and this is more of a fun trial build than an endgame weapon. (PSA you can get 100% status chance on a Zaw with Ekwana II links and 3 60/60's plus [Drifting Contact]).
Also both legendary mods obviously aren't required but they do increase the damage quite significantly.