If i remember correctly, the same mag said the banshee was 48 hp at the crank figure that means around 40ish for the shee and 42-44ish for the zilla at the wheels??  Those # dont sound too crazy to me.
I have a stock 87 zilla that i want to dyno just for hahas,  but i havent been able to locate an atv dyno anywhere remotley close to me.