There are three options available for you to export a list of users from your Zendesk account:
Use the Zendesk Rest API Users endpoint to capture the list of users from your account.
For Support Professional and Enterprise plan, export users in XML or JSON format. For more information about exporting data from your Support account, see the article: Exporting data to a JSON, CSV, or XML file (Professional and Enterprise).
Import to Nimble
Click your avatar in the top right hand corner
Choose Networks & Imports
From here, use the Import Wizard to upload your file.
For more information about this feature, please take a look at the following: