Zalando may have decided to no longer offer the cash on delivery option for various reasons. A key factor could be the digitalisation and efficiency of the payment process which facilitates the management of returns and refunds. Additionally, electronic payments are more traceable and secure, reducing the risks associated with carrying cash. You could also consider reducing operational costs, as cash management often involves a greater financial burden. Additionally, cash on delivery may slow down the delivery process as it requires payment verification at the time of delivery. Finally, limiting cash can be a measure to ensure the safety of couriers.