thanks is there a way to change the default 000webhost name servers?
What do you mean? There are two ways to link your domain: by parking (using 000webhost NS and then linking) or by CNAME records linking.
By linking your domain through CloudFlare you are required to use CNAME linking. If you use CNAME records you no longer need to park your domain, therefore no need to use 000webhost NSs. Use CloudFlare’s ones instead, as the tutorial asks