Explanation:
Hey there!
Given;

Looking through question, we can bring it to perfect square to remove the (√) sqrt.

We made this to bring it in the form of (a+b)^2. As (a+b)^2 = a^2 + 2.a.b + b^2.
Now, our question looks like similar to the formula.
So, We can write it as:

Now, we can cancel (√) and (^2). And we get
= z + 4
Hope it helps...