When opening CSV files in Excel, certain data that only contains numbers may get converted to a scientific notation automatically if they are very long to shorten it.

In the CSV file itself, all the numbers are there (you can confirm this by opening the file with a text editor). However, Excel and other spreadsheet software tend to auto-detect data by default which is causing the tracking numbers to be treated as a number instead of text.

In the spreadsheet software, you'd want the tracking number column imported as text. Another workaround is to simply add an apostrophe at the beginning of the data so it gets auto-detected as "text" in Excel and prevent it from turning it into a scientific notation.

You can do this in EZ Exporter by using a Custom Field like this:

'{{ fulfillments.tracking_numbers }}

Update: EZ Exporter also now supports exporting to Excel (.xls, .xlsx) formats directly which takes care of this for you automatically.