Microsoft Defender for Office 365 For Zoho Email Solution

Defender MDO is for Exchange Online only. In theory you might be able to set up a hybrid arrangement whereby some mails are then passed on from EXO to Zoho, but you are still paying one licence per address resolved on the EXO server. You might circumvent that by piling several aliases on each EXO seat, but the mails will be delivered to the primary address of each EXO account and you would need a horrible and probably unreliable arrangement to route them on to multiple Zoho addresses. You would not be able to send out using the multiple addresses, and if you are sending from Zoho Cloud-based Email Infestation then deliverability may be one problem you are trying to address. In any case your tracing and remediation features are unusable, making the whole idea of questionable value.