Figured it out. you have to format the string data as text. The data from the source cells must be put inside the text formula. For the zip code it should be:
=text(datavalue, "00000")
All US zipcodes are 5-digits long so the leading zero from the above example will be preserved. As for the number formatting, it also will be changed to text in order to preserve trailing zeros. For the number format, it should be:
=text(datavalue, ".00")
The data value above needs to be purged of commas before you can use this method however. The result will be placed in a cell and you should be able to perform math operations on it as well.