public with sharing class ApiCallOutUtility{

    

    //static String endpoint = 'https://accounts.zoho.com/apiauthtoken/nb/create?SCOPE=ZohoCreator/creatorapi&EMAIL_ID=gulshangupta90@gmail.com&PASSWORD=gulshangupta90';

    static String endpoint = 'https://accounts.zoho.com/apiauthtoken/create?SCOPE=ZohoCreator/creatorapi';

    static String username = 'gulshangupta90@gmail.com';

    static String password = 'gulshangupta1990';

    

   

    public static HttpResponse getCallout(){

        

            HttpRequest req = new HttpRequest();

            req.setEndpoint(endpoint);//'https://gwt56.zendesk.com/api/v2/users/me.json');

            req.setMethod('GET');          

            //Blob headerValue = Blob.valueOusername+ ':' +password);//'mo.usman786@gmail.com'+ ':' + 'G00gle@123');

            //Blob headerValue = Blob.valueOusername+ ':' +password);//'mo.usman786@gmail.com'+ ':' + 'G00gle@123');

            //system.debug('headerValue ::::::::' +headerValue);

            String authorizationHeader = 'BASIC ' + username+ ':' +password;//EncodingUtil.base64Encode(headerValue);

            system.debug('authorizationHeader ::::::::' +authorizationHeader);

            req.setHeader('Authorization', username+ ':' +password);//'226683dbdd982b812d78d5ac5dd9edda'); 

            req.setTimeout(60000);

            Http objhttp = new Http();

            if(!Test.isRunningTest()){ 

                HttpResponse res = objhttp.send(req);

                system.debug('res ::::::::' +res);

                system.debug('res.getbody ::::::::' +res.getbody());  

                    return res;

            }

        return null;

    }

}

Debug if giving the StatusCode = 303 . please suggest is this from zoho side.