Question 328249
First factor, then look for a difference of two squares.
{{{16z^4-y^4z^4=z^4(16-y^4)}}}
{{{16z^4-y^4z^4=z^4(4-y^2)(4+y^2)}}}
{{{16z^4-y^4z^4=z^4(2-y)(2+y)(4+y^2)}}}