Operates on Purchase Orders. In the Zuper client app this module is labeled "Purchase Order" for most companies, and "Material Order" for companies in the roofing industry — the API and data shape are identical either way. Purchase Orders and Work Orders (Service Orders) share the exact same underlying schema and endpoints; they're distinguished only by the purchase_order_type field (PURCHASE_ORDER here) and the /purchase_orders vs /service_orders route prefix. Creates multiple orders in one call. Each item in purchase_orders uses the exact same field shape as the single Create endpoint's purchase_order object (see Create Purchase Order / Create Work Order), just without the outer wrapper key.