Murai [6] obtained some important connections between height zero characters in the principal p-block and p-nilpotence of a finite group. In this paper, we generalize Murai's results to the π-block theory in a π-separable group,and prove that if π-Hall subgroups are nilpotent, then the intersection of kernels of π-height zero characters in the principal π-block is π-nilpotent; and then G is π-nilpotent if and only if π-height zero characters in the principal π-block are linear.Also, we obtain an equivalent condition for G being π-nilpotent by π-weights of G.