Sudoers
Add the user to the sudoers file:
sudo hx /etc/sudoers
Edit the following section and add your user below root and %admin.
# root and users in group wheel can run anything on any machine as any user
root ALL = (ALL) ALL
%admin ALL = (ALL) ALL
john ALL = (ALL) ALL
Admin Group
Check if user is an admin:
dseditgroup -o checkmember -m john admin
Add your user to the admin group (source):
sudo dseditgroup -o edit -a john -t user admin
Or you can create aliases in .zshrc:
alias isadmin="dseditgroup -o checkmember -m dryk admin"
alias makeadmin="sudo dseditgroup -o edit -a dryk -t user admin"