Yes, it is mandatory to map CSKU with iSKU. iSKU (Inventory Stock Keeping Unit) is a unique code assigned to a product to identify inventory assigned to the product. CSKU (Channel Stock Keeping Unit) is used while listing that product on various marketplaces (sales channels).
For some marketplaces, it is mandatory to mention specific description while listing the product. Hence, you can use different CSKU while listing same iSKU on various marketplaces.
For Lazada Marketplace
iSKU = MBL001 is listed with CSKU = MBL001
For Zalora Marketplace
iSKU = MBL001 is listed with CSKU = MBLRED001
Hope this answers your question!
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