I am trying to read through the proof of ELBO for diffusion models on pg. 8 of this paper. However, I do not see how the author arrived at Eqn (45) from Eqn (44). Specifically, I do not know how they simplified the equation by rewriting it in terms of the KL divergence. I do know the formula for KL divergence but it does not seem like a direct application in this case. Any help is appreciated. I have included an image below of the proof for convenience.