The phrase is correct, but jarring and overcomplicated
The phrase you're asking for, does join the three terms together in a grammatically correct way. However, it is a real mouthful to speak and most people would tend to a simpler alternative.
What you asked in the opening question:
I want to point out the relation[ship] between (A, B) and (C)
Works well to describe the situation.
That said, these phrases will likely suggest that there is a relationship between all three (A, B and C). Which is technically correct, but perhaps not the focus you want to give.
Instead, to focus on the specific relationship between (A,B) and (C) - I'd suggest a phrase along the lines of:
C's dependency on A and B
The dependency of C on A and B.
Which is a specific type of relationship - and conveys the specific situation more clearly.