If (2² = a²b² = za² + b² = z) and (ab = ya, b = y), which of the following is equivalent to (4⁸⁴ᶻ8y⁴)?

a) (2⁸⁴z + 4y)
b) (2⁸⁴z - 4y)
c) (2⁸4z + 8y)
d) (2⁸4z - 8y)