Zoho Mail / CRM with Mail Add on AND Google Apps

Zoho Mail / CRM with Mail Add on AND Google Apps

In Google Apps, I have one account called admin@mydomain.com and nickname called david@mydomain.com. So all e-mails going to david@mydomain.com is received in admin@mydomain.com mailbox.
 
In Zoho Mail/ CRN, I configured it where it will receive the admin@mydomain.com.
 
Question: I want to be able to send e-mail via Mail or CRM with a from address of david@mydomain.com. Right now, it will only use the admin@mydomain.com. Can I mask it somehow to say david@mydomain.com? Any suggestions?
 
Because I have clients thinking that my e-mail is admin@mydomain.com instead of david@mydomain.com
 
Thank you.