Syncing contacts on whatsapp

You can use iCloud contacts on WhatsApp but I don't think you can sync them.

WhatsApp is not an Apple product. Contact the app developer here --> App Support or WhatsApp FAQ  Or Restoring your chat history - WhatsApp FAQ or Contact WhatsApp

WhatsApp Business is not an Apple product. Contact the app developer here --> Developer Website  or App Support  or WhatsApp business products - WhatsApp FAQ

This may help you understand contact on an iPhone --> Contacts on iOS and iPadOS devices are synced to an email account… - Apple Community