I followed your advice and call Aeroplan again. This time the agent was more helpful. Initially, she said everything was okay; she just needed to get her supervisor to confirm the transaction. However, in the end it did not work. What needs to be done first, is to change the ZHR-DEL flight number from AC6826* to LX146. So I called Air Canada. They told me that the have to request the seat from Swiss Air and that might take up to 24 hours. So I have to call them again tomorrow.