Final answer:
The question seems to be about substituting and simplifying an expression with given values for y and z, but there is a lack of context that prevents providing a full answer.
Step-by-step explanation:
The question asked pertains to substituting values of y and z into an expression and then simplifying it. However, the provided information is fragmented and doesn't seem to match any standard mathematics problem format. With the given information, it's impossible to understand the full context of the expression that needs to be simplified with y = -3, and z = -7. If additional context is provided, we could potentially find the correct expression and perform the necessary substitutions and simplifications.