4(z-4)(z-4)-16
You can either distribute the 4 through the first binomial first or multiply the binomials first. I would probably multiply the binomials first:
4(z^2-8z+16) - 16
Then distribute the 4:
4z^2 - 32z + 64 - 16
Finally subtract the 16 from the 64:
4z^2 - 32 + 48