The zero-divisor graph of a ring R is a graph whose vertex set consists of all the elements of R and distinct vertices x and y are adjacent if and only if xy = 0. We study the zero-divisor graph Gamma(0)(& Zopf;(n)), for n = p(k), pq, pqr, where p, q and r are distinct primes. Topological indices such as Wiener and Harary indices of Gamma(0)(& Zopf;(n)) are determined.