I have a natural leven starter, but I am considering using this and some dried yeast in a bread to boost the process.
Is this possible or will one yeast kill off the other?
I see no reason why there should be any risk in using two types of yeast. Go for it. Just remember that for every amount of fresh you use you would use half that amount of active dry yeast and even less instant yeast.
One of my latest favorites breads uses 1.5 cup of starter and a packet of dry yeast.
My rye also uses starter and a small amount of dried yeast.
Some bakers use yeast to control the acidity of their sourdoughs - by introducing food concurrency
allows for a more predictable rise. I add some to the sourdough breads that I bake for sale, so that I know when they will be done. It doesn't affect the taste.