Plotting two related functions

I have two functions, X and Y. I would like to plot X vs Y, and I have a function Z such that I can write X(Z) and Y(Z). Unfortunately I haven't been able to substitute z into either such that I can write X(Y). I don't even think it's possible.

What can i do now to be able to plot a graph?

[dpb]

Z=f(???)

Use ??? to evaluate Z and put that into X,Y

Or if you have Symbolic TB, you can try symbolic solution.

W/O details, what are we to do?