> By using the Zenefits Service, you hereby grant us permission to access your Account Information maintained by identified third parties, and make changes to this information as directed by you, on your behalf as your agent. When you use the 'sync payroll' feature of the Service, you will be directly connected to the website or APIs for the third party you have identified. We will submit information including usernames and passwords that you provide to log you into the site. You hereby authorize and permit us to use and store information submitted by you (such as account passwords and user names) to accomplish the foregoing and to configure the Zenefits Service so it is compatible with the third party sites for which you submit your information.

So basically a user of Zenefits gives Zenefits the authority to act as an agent on behalf of them. So, technically when Zenefits accesses the ADP site they are legally seen as the authorized user themselves.

If I knew that a service was going to act on my behalf towards another party and that other party wasn't happy about the way that service behaved towards them. I might question my use of letting that service act as my agent.

Zenefits is actually pretty smart here because they can say "our users want this, they've agreed to our ToS that says we act on their behalf".