On endomorphism-regularity of zero-divisor graphs

The paper studies the following question: Given a ring R, when does the zero-divisor graph Γ(R) have a regular endomorphism monoid? We prove if R contains at least one nontrivial idempotent, then Γ(R) has a regular endomorphism monoid if and only if R is isomorphic to one of the following rings: Z2×Z2×Z2; Z2×Z4; Z2×(Z2[x]/(x2)); F1×F2, where F1,F2 are fields. In addition, we determine all positive integers n for which Γ(Zn) has the property.