Simplifying fractions with exponents

It should be simple, but I keep messing it up. I really need a step-by-step description of the process if it is possible, as the problem lies in my messing up one of the steps, I imagine, but I won't know which one(s) unless I see the correct steps.

Now, for the problem. __(-2xyz)-³__

(x²z-³)-³

The instructions are "Simplify".

Thanks sooooo much for any help!

P.S., I am homeschooled, and have the answer key. After checking the answer I realized that I have the numbers for the exponents correct, but I am somehow doing the coefficients wrong. Somewhere they are getting an "8x to the blah blah", and I have no idea how they got an 8?