You do not need to buy a domain from us to host with us.
AT CHECKOUT
Choose "Use a domain I already own". Enter the domain and continue. Nothing is billed for it.
AFTER THE ORDER
Your hosting account is created and the welcome email arrives with your cPanel details and your nameservers.
Then log in at your existing registrar and change the domain's nameservers to the pair shown for your account, either ns3 and ns4 or ns10 and ns11.zillionkinghost.com. Replace the existing entries rather than adding ours alongside.
WHILE WAITING FOR DNS
Build the site using the temporary URL in your welcome email, or add a hosts file entry on your computer so the domain resolves here for you only.
ORDERING WITH NO DOMAIN AT ALL
If you have not chosen a name yet, order with a domain you intend to register, or use the subdomain option where offered, and add the real domain in cPanel later.
WHY PEOPLE DO THIS
Keeping registration and hosting separate is a legitimate choice. Consolidating them with us is simpler to manage, but not required.