Where is Marx in the work and thought of Vygotsky?

What is it about the apparently clear question of Marx's place in the work and thought of Vygotsky that makes it so enigmatic? How should we understand the fact that the successive attempts to respond to this question over the course of a century have been so contradictory and remain so to this day? Before we attempt to resolve this question, is it not necessary first to ask ourselves what has made this into such a pitfall?