Frozen is frozen, whether it's with cold, terror, or both.

Chill of the Grave

This spell costs {1} less to cast if you control a Zombie.
Tap target creature. It doesn't untap during its controller's next untap step.
Draw a card.

Innistrad: Double Feature

Innistrad: Crimson Vow

Chill of the Grave costs {1} less to cast if you control any Zombies at all. It doesn't cost {1} less for each Zombie you control. If you control more than one Zombie, the spell still costs {1} less to cast.