  A ring R is a Zhou nil-clean ring if every element in R is the sum of two
tripotents and a nilpotent that commute. In this paper, Zhou nil-clean rings
are further discussed with an emphasis on their relations with polynomials,
idempotents and 2- idempotents. any a \in R, there exists e 2 Z[a] such that
a-e \in R is nilpotent and e^5 = 5e^3 -4e, if and only if for any a 2 R, there
exist idempotents e; f; g; h 2 Z[a] and a nilpotent w such that a = e+f +g+h+w,
if and only if for any a 2 R, there exist 2-idempotents e; f 2 Z[a] and a
nilpotent w 2 R such that a = e + f + w, if and only if for any a 2 R, there
exists a 2-idempotent e 2 Z[a] and a nilpotent w 2 R such that a^2 = e+w, if
and only if R is a Kosan exchange ring.
