When chosen Excel as XML publisher output, text with prefix zeros will be converted to number in excel output. To maintain the format
Option1
Change xml tag in template from
<?your_field?> to ="<?your_field?>"
Option2
Add NONBREAKING SPACE before the column.
Place cursor in front of the column you need press CTRL + SHIFT + SPACE. You can also choose this from menu.
Insert - Symbol - Special Characters.