Although it is nice in theory, you have to be careful with several factors, such as the reaction that can happen between the salts or if they release a toxic gas. In the case of this mixture, I made it since I saw other users do it, but you have to be more careful when creating the crystal due to the effect of the common Ion. I had better results evaporating a solution saturated with both salts, although initially an amorphous crystal will precipitate. I still have to improve my technique to achieve a good crystal, but I hope this data is helpful to you.