You can
put this solution on YOUR website! how do I factor 4y^2+9z^4?
That's the sum of two squares, since it can be written:
(2y)² + (3z²)²
Normally you can't factor the sum of two squares.
----------------------------------------------
In rare cases you can but this time you can't.
-----------------
If your problem had been
y4 + 4z4
instead you could factor it by adding and subtracting 4y²z²
y4 + 4z4 + 4y²z² - 4y²z²
Rearranging terms:
y4 + 4y²z² + 4z4 - 4y²z²
(y4 + 4y²z² + 4z4) - 4y²z²
(y² + 2z²)² - 4y²z²
[(y² + 2z²) - 2yz][(y² + 2z²) + 2yz]
or
(y² - 2yz + 2z²)(y² + 2yz + 2z²)
But that's an advanced factoring technique, and will
not work on the problem you had without using square
roots. So the answer to your problem is "It is a prime polynomial".
Edwin