What happen if I use pre increment and post increment in the same statement?

What happen if I use pre increment and post increment in the same statement?

I've seen an interesting statement today with post-increment and
pre-increment. Please consider the following program-
#include <stdio.h>
int main(){
int x, z;
x = 5;
z = x++ - 5; // increase the value of x after the statement completed.
printf("%d\n", z); // So the value here is 0. Simple.
x = 5;
z = 5 - ++x; // increase the value of x before the statement completed.
printf("%d\n", z); // So the value is -1.
// But, for these lines below..
x = 5;
z = x++ - ++x; // **The interesting statement
printf("%d\n", z); // It prints 0
return 0;
}
What's going on there actually in that interesting statement? The
post-increment is supposed to increase the value of x after the statement
completed. Then the value of first x is remain 5 for that statement. And
in case of pre-increment, the value of second x should be 6 or 7 (not
sure).

Why does it gives a value of 0 to z? Was it 5 - 5 or 6 - 6? Please explain.