Second Order Partial Derivatives

Just need pointing in the right direction then hopefullly I'l understand these (Headbang)....

Find 1st and 2nd Order Partial Derivatives:

z = 3x² - 2y⁴

First Order

= 2x

= -8y³

Now I know there should be 4 second order Derivatives and i remember how to work the first two out which are:

= 2

= -24y²

However I become stuck on working out the last two which I believe should be the same.

I know what they are they are the Zxy and Zyx and I know they are the same but could someone explain how i calculate these thanks.

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