If the four columns are already in Date/Time type, then you can compare the addition of the four columns directly and create a new column based on the results.
For example, if you're trying to check whether A+B > C+D and output true/false into a separate column, you can use a "New Formula" transform and set the formula to be
IF(A+B>C+D)
Since this creates a new column, remember to provide the new column with a name that best reflects the results of the formula.
If your field values are in something other than Date/Time type (e.g. String), then you can change the type of the column by clicking on the dropdown menu to the right of the column name > Change type > Date/Time