Usually you would say "improving the efficiency of x and y". In this case at the end of the sentence it should be "improving the models' efficiency" or just "im

Usually you would say "improving the efficiency of x and y". In this case at the end of the sentence it should be "improving the models' efficiency" or just "improving efficiency". I don't think it's "wrong" and it's obviously clear what they mean, but I agree that the phrasing is a little awkward.