To add support for S3 Express One Zone bucket in Skypilot, you may need to make changes in the create_s3_client function and the S3Store class. Specifically, you may need to pass the endpoint argument when constructing the client in the create_s3_client function, and make any necessary changes in the S3Store class. Additionally, you can submit an issue on the Skypilot GitHub repository to track this feature request.