Verified answer

Use exponential properties...

(aⁿ)^b = a^(nb)

aⁿ/a^b = a^(n - b) - 1/a^(b - n)

a^(-n) = 1/aⁿ

So you get...

(16)^(¼) * y^(-4 * ¼) * z^(8/4) * 1/[(64)^(1/6) * y^(6 * 1/6) * z^(-12 * 1/6)]

= 2y^(-1)z²/(2yz^(-2))

= 2z^(2 - (-2))/y^(1 - (-1))

= 2z^4/y²

I hope this helps!