As of the date of this article Gazelle does not offer a Xero integration. This is on our development radar (especially for our customers outside the United States where Xero is more popular than QuickBooks Online).
If you use Xero Accounting products and switching to Quickbooks Online isn't an option, then please email support@gazelleapp.io with the subject line 'Xero Accounting Integration'. If we have enough demand for this product we will reevaluate our timeline for prioritizing this feature.