Can I disconnect our WhatsApp number from Facebook Business Manager and then reconnect with a different FBM? Follow

No, it is not possible per Meta rule. You can connect it back to the same FBM after disconnecting it but not to a different FBM.

Whether re-connecting the number with Zendesk or transferring it to Freshdesk or other providers, it's the same number=same FBM ID.

As for reconnecting the number to the same FBM, it is possible, however, aside from taking the number offline, you need to go through the same process when it was activated.