Converting a Crystal Report Formula to a CASE expression
It looks as though "order_no" is not used a reference for the CASE expression unlike the formula. With making some minor tweaks and replacing my "+" in my sub CASE with "/" I received the correct outcome.

CASE WHEN (SUM(TCT.[weight]) + SUM(TPM.[weight])) &gt; 0
     THEN
        CASE WHEN (SUM(CONVERT(DECIMAL(10,4), (TRCB.skid_height_inches * 
             TPM.dim_ext_x * TPM.dim_ext_y) / 1728))) &gt; 0 
             THEN (SUM(TCT.[weight]) + SUM(TPM.[weight])) / 
             (SUM(CONVERT(DECIMAL(10,4), (TRCB.skid_height_inches * 
             TPM.dim_ext_x * 
             TPM.dim_ext_y) / 1728)))
             ELSE 0
        END
     ELSE 0  
  END AS 'TOTAL_PCF'