Zimbra Split domain configuration zimbra is secondary

I am looking for a freelancer to assist me with configuring split domain on my Zimbra server. We have already configured Zoho to Zimbra, whatever the emails we send from Zoho to Zimbra are coming, but not working from Zimbra to Zoho. Zimbra & Zoho to external communication is happening absolutely fine. My Zimbra version is 9.0 opensource, and we have configured spamexperts antispam relay to the primary zoho, outgoing we are sending from Antispam cloud. Ideal skills and experience for this job include:

- Expertise in Zimbra 9.x
- Experience with split domain configuration with Onpremise Zimbra email server
- Ability to troubleshoot and resolve email delivery issues.
- Familiarity with spamexperts relay configuration