How do I run multiple zip files unzip through ant script using for loop? I didn't get any output.

Code:
<?xml version="1.0" encoding="UTF-8"?>
<unzip dest="D:\">
<fileset dir=D:\>
 <echo message="The unzip the files:"/>
<for list="**/*" param="letter">
 
</for>
</fileset>
</unzip>
...