using Linq
List<decimal> listA = new List<decimal>() { 1.5M, 2.63M, 1.25M };
List<decimal> listB = new List<decimal>() { 2.5M, 0M, 1M };
List<decimal> listC = listA.Select((dValue, index) => dValue * listB[index]).ToList();
This uses the form of Linq 'Select which automatically creates an index for you [
^].
Note that this would fail if ListA had more elements than ListB, but work if ListA had fewer elements than ListB. You may want to put a test in your code to ensure both lists have the same number of elements ?