al length into one iterator of
  two-tuples, where the first element of each tuple is taken from the
  first iterator and the second element is taken from the
  corresponding element in the second iterator.</td></tr>
<tr><td valign="top"><a href="#zip3-3">zip3/3</a></td><td>
  "Zips" three iterators of equal length into one iterator of
  three-tuples, where the first element of each tuple is taken from
  the first iterator, the second element is taken from the
  corresponding element in the second iterator,