Q: Can one Team leader or similar manage all the teams' accounts?

A: Each user will need their own account in Zaplify, but as long as the team leader has access to the other users' login details, they can manage all users by switching user logins in Zaplify.

However, if you are using Google sign-in, it is not possible to sign in to your account without having access to your Google account. That is for privacy reasons. Your manager should have their own account where they can access all statistics to track the progress.