“If all is emptiness, from whence do these forms arise?”

They don’t. Forms appear to be present; in truth, they are not. Consider: in a mirage, a pool of water appears to be present; but it is not, in actuality.

The question is posed from the standpoint of the “individual”, not from the standpoint of emptiness.

If all things are empty, “you” are among one of those “all things”. And equally empty are any “other” forms that are conceived by you. Since you appear to be “real”, all that you perceive appears also to be real. The actuality is that you are empty and all forms perceived by you are equally empty.

So not anything ever actually “arises” from emptiness: emptiness is, and always has been, 100% empty of anything. 

All that is seen—as well as the seer—is empty of reality. There is only “what is”, and in reality it “isn’t”.