I learned that the output of hash function from Merkle Damgard is
H(x) = ZB+1 = h(ZB || L) = h(ZB - 1 || XB || L) where XB = block of padded x and L = XB+1
and it is proven that H(x) is collision resistant. However, what if I tweak the H(x) by extracting L from the compression function h(x) s.t
H(x) = h(ZB - 1 || XB) || L
I feel like this makes H(x) to be not collision resistant, but I don't know how to design an attack for this hash function. Can someone give me an idea (perhaps hint) to design such attack?
NOTE: Before anyone screams at me about anything, I want to say YES this is a practice question from a cryptography textbook. That is why I asked for a HINT not an answer. Thanks :)