On page 167 of the Beastiary 2, the Inevitable Zelekhut is CR9.
That seems too low to me.
There is nothing this guy is not good at. Excellent AC, DR10/Chaotic; SR20; they're Constructed (immune to a bucketload of effects); Can cast Fear and Hold Person at will; Constant True Seeing; 10' Reach; Speed 50' Fly 60'; Dodge, Mobility, Vital Strike; and two excellent Melee attacks that trip.
Does that seem like a CR9 guy to you?
I think it's fairly similar in power level to other CR 9 creatures, such as a bone devil, a dragon turtle, a greater air elemental, or a young bronze dragon.
Edit: It's probably in the upper tier of CR 9 monsters due to the lack of obvious weaknesses, but I don't think it's sufficiently powerful to match most CR 10 monsters.