Impossible. Athena can only READ a bucket from a different AWS account and region, not WRITE.

Sources:

Create a query output location - Amazon Athena

Using the same AWS Region and account that you are using for Athena, follow the steps to create a bucket in Amazon S3 to hold your Athena query results

The results bucket must be in the same region AND the same account as Athena.

Troubleshoot "Invalid S3 location" error when saving query results in Athena

Verify that the S3 location where the query results are saved is in the same Region where you run the queries.

...

The S3 query result location that you specified is in a different Region.

Listed as one of the error causes.

In conclusion: AWS explicitly requires that the output location be in the same region AND the same account.