Dividing powers with the same base?

I wasn't sure exactly were to post this because its actually apart of a logarithm i'm trying to do,

The bit thats troubling me is I have to divide

7z^3 by z^2

(I just using ^ for a 'power of' symbol)

Now I know when dividing powers of the same base you simple take them away from each other e.g. 3 - 2

But the fact that the first number is 7z and the second is just z are they still the same base? can I apply this theory?

Help greatly appreciated, got an exam next Monday >_<