Big Horns and Zillas are two completely different types of tires. Big Horns are designed for trail riding in hard pack, rocky terrain & loose dirt. They give you a very smooth, plush ride with very little feedback in the handlebars. Zillas are designed for wet, sloppy, muddy conditions. They will do anything a Big Horn will do but with more handlebar feedback, a little more vibration, and a far less ride quality.
To be honest, I wouldn't even compare two.