Ask HN: What's the best way to manage clients' credentials?

How do you keep track and securely manage the credentials of a number of clients. I'm talking about credentials for web hosting services, web apps, other kind of services/account installed/opened on behalf of the client.

I have all them scattered into password managers and backed up into encrypted zip files, but I feels there should be a better organized way to do that.

So, what's your way?

Thanks