The Miracle of the House of Brandenburg, I mean. Prussia was about to be utterly crushed by the combined Austrian-Russian forces when the sudden death of Elizabeth and the accession of Peter III caused Russia to withdraw from the war, subsequently leading the Anglo-Prussian side to victory.
Suppose, instead, that Elizabeth had never had her fatal illness, or had survived for several more weeks. Fredrick II is killed in battle, Berlin is occupied. What happens afterward?