I have zd326 - took it on heavy slope- tip meter cut it off. So now, no power, no fun, nose pointing down hill, slid down with parking brake.
any of the caster front wheels have trouble holding a slope.
I will vouch for my machine over most on most terrain. The Kubota is a horse that has never bogged down, but I don't like it on a slope- and it may just be my scaredy cat factor. On the real steep slopes (think slope so hard to walk) I use a Honda propelled with oil pump. it is mac daddy.