To make the above equation valid replace each of the four ? marks by any operator of the set (+, -, /, *) and unlimited quantity of brackets.

Rem1: No other operators/signs allowed.
Rem2: Analytical solution preferred.

Somehow, I omitted the "D4 bonus question: "What if each operator i.e.    + - * /  is to be used once only and only one pair of brackets allowed?"

Fortunately, your program found it:  

 (2/3-4+5)*6