Financially? In a word. NO!
You will never be able to sell a restored Z for what it costs to restore it. Think about it, how many times have you seen have $20K invested, will sacrifice for $4k or something similar?
I restored my '77, doing all of the work myself. Parts and paint came to greater than $7K. If you paid someone to do the work, it would cost another $8-9K at least. Could you sell the car for greater than $20K when you are done? I don't think so!
If you are going to keep the car for yourself and drive it, then it might make sense.
The only time a restoration make financial sense is if the car is a highly desirable collectable like an early corvette, a Ferrari, or some other special interest car. Unfortunately, I have yet to see any Z car in that category.
Do what the car was meant to do. Get it running well, looking good, and DRIVE IT!
Enjoy you Z!
Patrick Robinson