Yes, you can use Outlook as your mail application instead of Zoho.

Zoho Mail is the platform and infrastructure that we supply to our customers. We recommend that you use the native webmail and desktop and mobile apps. However, if you'd like to use Outlook, or any other 3rd party mail app, you can do this by following the instructions in this tutorial: Connecting your mailbox to other email software.

It is also worth reading our rationale for why using the native apps we provide is recommended: Reasons to use our Zoho Mail solution instead of IMAP with external mail apps