hey, i used to play on evil biomes and most of the tricks i learned come from "furnace clan" (a series you can find on youtube).
First, if you don't have one, you need a pit with magma at the bottom. either by digging all the way down, or by getting magma up. in any cases it's best to have upright spears at the bottom. Now you can have you dump zone to throw stuff in the pit. that should take care of severed limbs before they res up. (you need to be quick with the dumping.)
You also need to favour hammers, maces and spears for extreme cases. avoiding severed limbs is best.
(btw if it's not clear enough you should seal up your dworf right after embarking)
Fun fact: zombie alpaca skin is magma-proof. If you pit it into a volcano it will survive the magma, survive impact with semi-molten rock, and crawl around down there burning forever but not dying. The only way to get it to stop smoking and probably eating FPS is to drop a cave-in down the volcano on top of it.
You can build an atom-smasher but that won't smash skins of really big creatures. Cave-ins or obsidianizing are the only sure kills.
Dwarves attacking a skin are not that bad. I've used them as training dummies. Deactivate the squad and create a burrow that doesn't include the skin, and then it follows your retreating dwarves over a cage trap.
Visitors attacking a skin are bad, and will surround and punch a zombie skin forever while ignoring orders. The solution is to design your fort so that butchering happens far, far away from common areas and right next to your cave-in/magma disposal system.