Learn by reading this example:

#cat .htaccess

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} ^blog.droidzone.in$ [NC]
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://blog.droidzone.in/$1 [R,L]
RewriteCond %{HTTP_HOST} ^supernova.droidzone.in$ [NC]
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://supernova.droidzone.in/$1 [R,L]
RewriteCond %{HTTP_HOST} ^(.*)droidzone.in$ [NC]
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://droidzone.in/$1 [R,L]
</IfModule>

[NC] Ignores case.
Consecutive RewriteCond statements have an implicit AND.
The RewriteRule applies to the RewriteCond immediately preceding it. The rest is apparent.