I expect AC will try to weasel out of the compensation by blaming weather. The aircraft went MEX-YYZ, YYZ-ZRH, ZRH-YYZ, and it was already very very late into YYZ from MEX, for which weather was blamed. However, both YYZ and ZRH had light snow at worst, with average delays <60 min, not 5+ hrs.

Just the delay on AC145 alone would entitle me to max compensation, let alone AC881 being late and AC157 cancellation, so if AC is uncooperative I'll likely hand over the whole thing to Airhelp.