Google is a registrar themselves... Do you mean they use someone else for their own domains?
Domain Name: GOOGLE.COM
Registry Domain ID: 2138514_DOMAIN_COM-VRSN
Registrar WHOIS Server: whois.markmonitor.com
Registrar URL: http://www.markmonitor.com
Updated Date: 2018-02-21T18:36:40Z
Creation Date: 1997-09-15T04:00:00Z
Registry Expiry Date: 2020-09-14T04:00:00Z
Registrar: MarkMonitor Inc.
Registrar IANA ID: 292
Registrar Abuse Contact Email:
abusecomplaints@markmonitor.comRegistrar: Google Inc.
Registrar IANA ID: 895
Registrar Abuse Contact Email: registrar-abuse@google.com
Registrar Abuse Contact Phone: +1.8772376466
Verify yourself at: https://www.iana.org/assignments/registrar-ids/registrar-ids...
Zoho is Zoho Corporation Private Limited IANA ID: 3803
"Cloudflare Registrar is the highest level of registrar security. It protects your organization from domain hijacking with high-touch, on and off-line verification of any changes to your Registrar account. Cloudflare is an ICANN accredited registrar providing secure domain registration for high-profile domains."