$\sqrt{(x + y)(x + z)} + \sqrt{(x + y)(y + z)} + \sqrt{(z + y)(x + z)} \geq x + y + z + \sqrt{3xy + 3yz + 3zx}$
This is a very challenging question. It should be offered a fair bounty.
This is a very challenging question. It should be offered a fair bounty.