[Answer]-Best way to show two fields of one related object in ModelAdmin

It’s unclear what you’re asking. Do you need something different from the default Django model admin as documented here:

https://docs.djangoproject.com/en/dev/ref/contrib/admin/#modeladmin-objects

Edit:

In that case, you’ll want to modify the form used in the modeladmin, probably the easiest way to do this is with modeladmin.get_form() and then formfield_overrides to change the widget.

https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides