If you export data with zip code fields and try to import that data into Excel or most any spread sheet program, you will have a problem if your zip code starts with a 0. Excel will think it is a number and simply remove the extraneous 0 from the beginning leaving you with an invalid 4 character zip code.
There are two ways to fix this problem,
1) select the column of cells with zip codes, right click and select Format. Then select a numeric format, choose a custom format and in the "Type" field enter: `00000` (5 zeros). (See this [video from Microsoft for help creating a custom numeric format.)](https://support.office.com/en-us/article/Create-or-delete-a-custom-numbe...).
2) Select the column or block of zip codes. Go to the Number Format dropdown box (usually on the HOME tab). Select "More Number Formats"; Select "Special"; Select "Zip Code".
When displaying your data, any field with less then 5 numbers will have a 0 pre-pended.