A religous zelot friend how would you deal with him?

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A friend of mine converted from Christianity to Islam. Despite I respect his decision, he always tries to convince me that his religion is better than mine. He knows that I am convinced in my religion and I won't follow in his steps. We are ending up arguing most of the times that we meet. It seems that religion is on top of his agenda at the detriment of our friendship. How would you react?