Oh, wait, do you mean the machine like box with the huge arms that stretch out horizontally? Hammer it (and the other machines) with lightning. Be sure to get haste put on your characters first, and it doesn't hurt to buff up your characters magic, either. Get it to break (I forget the word for this, I think it was break...) and then just hit it with your physical attacks and it should die pretty easily. Basically, you want to be quick and heal rarely. The smaller guys should be a piece of cake but they will constantly be regenerated when they are killed, so I would focus more on the big guy than the little ones.

I would say more but this is all going purely by memory. It never hurts to do a Libra at the very start of battle so that your characters don't waste time using fire, ice, etc. when all they need is lightning. It also helps to use one of those items that automatically puts your characters onto haste at the start of battle.