What is the ruling on the supplication: "O Allah, if this matter is good for me, then decree it for me, and make it easy for me, and then bless me in it. And if it is not good for me, then make it good for me, then decree it for me, and make it easy for me, and then bless me in it"?

There is no legal impediment to supplicating for the transformation of evil into good, for Allah is capable of that, such as making the fire cool for Abraham, and the belly of the whale safe for Jonah. However, it is preferable to ask Allah directly for good without affectation, as in the Du'a of Istikhara, and the supplication for seeking all good and seeking refuge from all evil, and asking for every decree to be made good.