I have tried to install through many mirrors but many of them take more than half an hour to install the full OS. During the start of installation, it shows 10-15 mins time, then a minute later it shows 30-40 mins time. Also, kindly let me know whether its a network problem or mirror problem or computer problem.
deb http://in.archive.ubuntu.com/ubuntu/ focal main
deb http://in.archive.ubuntu.com/ubuntu/ focal-security main
deb http://in.archive.ubuntu.com/ubuntu/ focal-updates main
for the India repos - for the Zorin specific packages i don't believe there is a India hosted repo but for the core os, and applications those repos will make things a bit faster for you