Fully simplify and write your answer in exponential form with positive exponents only. Example: 153\frac{1}{5^3}

To simplify the expression \(\frac{1}{z^{8}} \cdot \frac{1}{z^{4}}\), follow these steps:

1. Rewrite the expression by combining the fractions:
\[
\frac{1}{z^{8}} \cdot \frac{1}{z^{4}} = \frac{1 \cdot 1}{z^{8} \cdot z^{4}} = \frac{1}{z^{8 + 4}} = \frac{1}{z^{12}}
\]

2. Since the goal is to express the result in exponential form with positive exponents, you can write:
\[
\frac{1}{z^{12}} = z^{-12}
\]

However, since you've asked for a positive exponent, we can rewrite it as:
\[
z^{12} = z^{-12}
\]
But in this case, we realize we have been given instructions not to express with negative exponents, so we will retain it as:

\[
\frac{1}{z^{12}} \text{ or } z^{-12}
\]

Since the expression was to be expressed positively, and you already have the term as \(\frac{1}{z^{12}}\) is indeed indicating a positive representation in terms of \(z^{-12}\).

Final Answer:
\[
\frac{1}{z^{12}}
\]