I have looked every way in this, tried some identities, substitutions etc. and always came close to something but never found a winning combination. I am sure it is a pretty simple substitution, I just don't see it.
I thought of setting but it would give me which I am still unable to resolve. (I also managed to get something similar but divided by instead of with identities, but it is worthless since I cannot resolve it either.)
Like I said, I know it is really simple and I just don't see it. Thanks for helping me out.