Chris,

 

Yes, here are the solutions:

1. Call zoom function in the client side.

    var editor1 = document.getElementById('<%=Editor1.ClientID%>');
    editor1.ExecCommand("ZOOM",false,75);

2. Call zoom function in the server side.

       StringBuilder sb = new StringBuilder();
       StringBuilder aSetPosition = new StringBuilder();
       sb.Append("<script language='javascript'>");
       sb.Append(" var editor1 = document.getElementById('"+Editor1.ClientID+"');");
       sb.Append(" editor1.ExecCommand('ZOOM',false,75);");
       sb.Append("</script>");
       Page.RegisterStartupScript("zoom", sb.ToString());