Conditional column calculation (If-Then)

Hi,

I have two columns, where the majority of the data are the same, but there are a few entries in one column that are 0 and the correct amount is in one column and vice versa

My initial thought was to simply add the values into a new column, but that would double up the entries were same values were entered in.  Is there a way to have it, so that if the first column is zero, it would show the second column, and vice versa?  Maybe some sort of If-Then condition?