It take me a little bit of time to create this :
Let $a,b,c>0$ such that $a+b+c=1$ then we have : $$\sqrt{\frac{(ab)^2+(bc)^2+(ca)^2}{a^4+b^4+c^4}}\Big(\sum_{cyc}\frac{a^2}{7a+5b}\Big)+\frac{(a-b)^5}{12}\leq \frac{1}{12}$$
First of all we have two equality case when $a=b=c=\frac{1}{3}$ and $a=1$
I have tried to delete the square root and after a full expanding to achieve with the Buffalo's ways.But I cannot conclude since we have negatives terms .I have not try Lagrange multiplier because I'm not familiar with this method but I think that the system resulting is awful .
If you have a trick (maybe with Cauchy-Schwarz) or a good answer I accept .
Thanks a lot to all .