Upper and Downers? I wouldn't mix, cocaine is a strong stimulant, and hydromorphone is a strong ass opiate lol I don't know your tolerance, but honestly I wouldn't do it, depends on how much of each you plan on doing.
HR answer- it is not a safe combinations, as common sense tells ya (as noted above: uppers and downers is bad on more than one main organ in the body). However, if you just search that combination (which is really quite common) you will find that many people injest the two very often. *Also, knowing what your body has handled in the past as well as doses/specifics you were taking would help in getting you a good reply.