You are correct; use a 1/2 drive ratchet/breaker.....I don't know of any other tool that works well on a real tight diff plug on a zed....if usings a 1/2" ratchet, make sure its a heavy duty one, because yes, you could trash it, sometimes these are on tight, and like I said previously, make the ratchet longer for leverage.

..........and use anti-seize compound on the threads of the plug before you reinstall it.

I changed my 5 speed gear oil and differential oil this weekend.  It was not really that bad, except getting the differential fill plug back in is annoying once it is full of new oil and dripping out.