Find 2x2 − 2z4 + y2 − x2 + z4 if x = −4, y = 3, and z = 2.

If you put in the substitutions it would be 2*2-(2*2*4)+(3*2)-(-4*2)+(2*4).
Simplified further by multiplying it would be 2*2-8+6--8+8
the negative 8 could be simplified further since the negatives cancel out so you'll have 2*2-8+6+8+8.
Then using the order of operations you would multiply the 2's together first to get 4 so you have 4-8+6+8+8. 
After that it's simple addition giving you an answer of -26.
I'm not sure if you're looking for the final answer or just the equation with substitutions but there's both.