Solution - Simplification or other simple results

Reformatting the input :

Changes made to your input should not affect the solution:

 (1): "c3"   was replaced by   "c^3".  2 more similar replacement(s).

Step  1  :

Checking for a perfect cube :

 1.1    a³-3abc-b³-c³  is not a perfect cube

Final result :

  a3 - 3abc - b3 - c3