When Cainiao and 4PX are unable to ship your package, we will use this logistics provider. However, it is a bit unique.For shipments to the U.S., after we dispatch the package, you will receive a tracking number that starts with "ZL" This tracking number will not provide any tracking information for the package. After 1-2 days, we will update the original tracking number to a USPS tracking number.Until USPS receives the package, the tracking status will remain as "USPS Awaiting Item," with no updates. Once USPS receives it, the status will change to "Accepted at USPS Origin Facility," and you will be provided with an estimated delivery time. After that, you'll just need to wait for USPS to deliver the package to you.