How to bulk update the custom account type for relevant natural account values?

Summary:

Bulk update of custom Account Type 'Statistical' in Manage Chart of Account Value Set Values page.

Content (please ensure you mask any confidential information): We have created a custom account type called 'Statistical' (with lookup code 'Z') in our implementation (attached snapshot). Now we are exploring the option to bulk update this custom account type for those accounts for which we created this type. Since our values are huge in numbers so we thought of doing it by regular FBDI for values & hierarchy but it is not accepting as it throws error if are trying to input 'Z' in the FBDI (attached snapshot). We don't want to do it by manual approach of going to instance and updating one by one as it