How to change the expense report approver?

Summary:

A manager needs to remain set as such, but the approval for expense reports of his subordinates needs to be done by another employee.

Content (required):

Hello,

It is a manager (zzz) that claims he does not have access now to the application.

He really is the manager of employee ****.

**** needs to have the expense reports approved by yyy.

The setup is created to take the manager for the approval task, which is zzz.

How can be changed the approver of the expense reports of **** to go to yyy, without changing the manager in the system?