If you make the proper request to the zerotier central API, then you can add your client id, and then when you join the network it will be already authorized.
using the example found here you with curl
curl -X POST -d '{"config": {"authorized": true}}' -H "Authorization: bearer <API_auth_token>" https://my.zerotier.com/api/v1/network/<network_id>/member/<client_id_to_authorize>
if you then joined the network with the same client_id_to_authorize then you shouldn’t have to authorize them in the UI