If you changed the passports in the 5 year eligibility period you have to share the details of all the passports. It clearly mentions in the application form.
No offense, please read the above post carefully, his new passport will be out of the 5 yr eligibility period.
But Still he will have to show both the passports at the citizenship interview;
his old passport for time spent in Canada during the eligibility period and
the new passport to show current nationality as the old one will be expired and invalid.