for the zazami, monoblos crab, you can only break is monoblos skull (2 times), but only with a blunt weapon like Hammer (that's mostly all...)
for kut ku just have to smash his head into to step. For the first part it will protect his ear buy lower it. then just have smash once more to explode his ears. but every time I tried I killed him before succeding smashing his ear
Then for most other monster, 3 part are breakable, with nothing special to do. Only tails need slashing weapon, like sword or great sword, but arrows too, to be cut