Recommended approach:

• Segment at the source level using geography filters (Author Country, Profile Location, or Source Country), rather than post‑processing the data.
• Create separate listening segments (or saved searches) for Australia and New Zealand using the same keywords, topics, and rules to keep the comparison clean.
• Use structured location signals first (author country, page country, channel metadata) before relying on free‑text location fields.
• Apply identical filters and date ranges across both datasets to avoid skewed results.
• Validate data quality by sampling posts from each segment to confirm location accuracy.

Common pitfalls to watch for:

• User‑entered location fields can be incomplete or inconsistent.
• Global publishers or syndicated content may need additional exclusions.
• Language filters alone won’t reliably separate AU vs. NZ content.

If you keep topic logic identical and isolate geography through dedicated segments, you should be able to run accurate side‑by‑side comparisons without compromising data integrity.