How do you Factor t^2 + 4z^2

Answer 1

you can't in general, using real numbers.
t^2+4z^2 = (t+2zi)(t-2zi)

If you have a typo and meant

t^2 - 4z^2, that is (t-2z)(t+2z)

Answer 2

y^3+y^2-4y-4