Real-Time HubSpot-Xero Invoice Sync

I need an integration that keeps invoices fully aligned between HubSpot and Xero in both directions, updating instantly whenever a record is created, edited, paid, or voided in either system. Only invoice data is in scope for now; contacts and deals will stay untouched.

The job is complete when:
• Every invoice added or modified in HubSpot appears in Xero with identical line items, tax codes, payment terms, and reference numbers—and vice-versa.
• Status changes (sent, paid, void, etc.) propagate within seconds without manual refresh.
• Duplicates are prevented through reliable ID mapping.
• A simple audit log or dashboard shows the last run, success messages, and any errors with clear retry options.
• I receive concise setup documentation so I can reconnect the integration if API keys change.

I am open to your preferred method—native APIs, a lightweight serverless function, or a low-code connector such as Zapier, Make, or Workato—as long as it meets the real-time requirement and can scale with volume spikes at month-end.

Let me know your proposed approach, estimated timeline, and any past projects that prove you can keep HubSpot and Xero talking smoothly.