Shearan's face lights up for a second. Something just occured to me. Jarik, you said you know some offensive spells? If you start blasting the zombie, it should try to get at you, but if it flies badly, it take long enough to get there that we can hit it with the nets. Then we just have to keep shooting and blasting it till it's inanimate. Oh, and since it is a zombie, it's wounds do not heal without magic, so if we down it with nets, we have a very long time to kill it.
Shearan then turns to the farmers. Speaking from experence fighting Karrnath, this abomidation is most likely not immune to arrows. It's more like resistant to any sort of piercing weapon. A longbow or heavy crossbow should hurt it fairly consistantly. For that matter, a light crossbow might work, although it's hard to tell with this type of undead, since they aren't smart enough to feel pain.