Weaken guarantee around advancing underlying iterators in zip

library/core/src/iter/traits/iterator.rs

@@ -457,8 +457,10 @@ pub trait Iterator {
     /// In other words, it zips two iterators together, into a single one.
     ///
     /// If either iterator returns [`None`], [`next`] from the zipped iterator
-    /// will return [`None`]. If the first iterator returns [`None`], `zip` will
-    /// short-circuit and `next` will not be called on the second iterator.
+    /// will return [`None`].
+    /// If the zipped iterator has no more elements to return then each further attempt to advance
+    /// it will first try to advance the first iterator at most one time and if it still yielded an item
+    /// try to advance the second iterator at most one time.
     ///
     /// # Examples
     ///