To simplify the expression \((1/3)^6 \cdot (1/3)^3\) using the Product Rule of Exponents, we can use the rule that states:
\[ a^m \cdot a^n = a^{m+n} \]
In this case, \(a = \frac{1}{3}\), \(m = 6\), and \(n = 3\). Applying the rule:
\[ (1/3)^6 \cdot (1/3)^3 = (1/3)^{6+3} = (1/3)^9 \]
Thus, an equivalent form of the expression \((1/3)^6 \cdot (1/3)^3\) is:
\[ \boxed{(1/3)^9} \]