I'm trying to figure out how to solve this, apparently it's hashing the hash value itself. So G has two rounds of hashing the original message x. I tried searching for the relationship properties that I could use to achieve this
•Collision resistance implies 2nd-preimage resistance
•If the output values of 𝐻 are uniformly distributed, then collision resistance implies preimage resistance
•If the output values of 𝐻 are uniformly distributed, then 2nd-preimage resistance implies preimage resistance
•Preimage resistance does not imply 2nd-preimage resistance
•2nd-preimage resistance does not imply collision resistance
But I didn't find anything I could use, I'm really having trouble, so I'd appreciate any help.