You may have Deathcoil Wurm assign its combat damage as though it weren't blocked.
4/27/2018 You can decide to assign damage to the defending player or planeswalker even if the blocking creature has protection from green or damage preventing effects on it.
4/27/2018 When assigning combat damage, you choose whether you want to assign all damage to blocking creatures, or if you want to assign all of it to the player or planeswalker this creature is attacking. You can’t split the damage assignment between them.
4/27/2018 If blocked by a creature with banding, the defending player decides whether or not the damage is assigned “as though it weren’t blocked”.