Bring pickaxes and farcaster (If you want to, you can also bring book of combos and the
combinating items for more farcaster)

Go to area 8 from area 7, check the walls on your right. There's supposed to be a small
passage which you need to crouch to enter it. After you jump down and climb the high
cliff, on your right there's a shedded skin of Kushala daora. Use your pickaxes here and
you will obtain khezu whelps. However, bringing this thing on your bag will gradually
decreases your health bar. I suggest to use farcaster immediately after you got the khezu
whelp. You can only carry one khezu whelp, so deposit it to the red box and repeat the
process.

First kill kezu in quest then curve it!

Um, unfortunately, no. You can't get Khezu Whelps by killing a Khezu or carving it
(Reference : MH Wiki and gaming experience)