I've just submitted v3.1.1 of VAT4EU for the Zen Cart moderators' review; I'll post back here when it's available for download.

This release contains changes associated with the following GitHub issues:

#16: Correcting integration with Edit Orders, v4.6.0+.
#17: Use zen_cfg_read_only to ensure that the version number is read-only.
#18: Correct strict comparison that resulted in incorrect message to customer.