I have had instructions shown below to delete the records listed below in order to use my Zoho e.mail A/C.
Is it OK to do this or will it in some way alter the security of the go daddy web site I own?
We still see that the MX record for your domain is pointed to both Zoho and Go daddy.
We request you to login to your DNS management page ( Go daddy ) and remove the old MX records ( smtp.secureserver.net and mailstore1.secureserver.net ) and keep only Zoho MX records to receive emails in Zoho. Please refer this help page to know how to configure MX records.
MX records just define where email should be sent to, so removing non-Zoho entries just means mail won't attempt to be delivered to GoDadddy should Zoho be unavailable. It doesn't affect HTTP(S) requests for web sites.
If you use SPF, then you will need to make sure this TXT record is also updated to reflect authorising Zoho to send emails on behalf of your domain.