Deductions & credits

Thank you for your response! 
I should probably clarify that I only bought 2 sliding doors. 
The sliding doors that I purchased replaced two existing windows and 2 existing doors. This sliding doors are very big (covering walls that had prior windows and doors).  
my question is — can I split the cost for the two sliding doors between doors and windows to maximize my credit given I replaced old windows and doors? Or, regardless of what I replaced I can only get credit for two sliding doors?