According to one of HCQ's earliest and most spectacularly successful proponents, Dr. Vladimir Zelenko, HCQ + Zinc is to be used on high-risk patients (older, comorbidities) as early as possible, on the same day as the COVID-19 test or immediately upon the onset of symptoms. The whole idea is to prevent the cascading ARDS events which result in high-risk patients' hospitalization, not to intervene after ARDS and critical hospitalization.
Here's a group of Brazilian scientists and academics who charge that (some) doctors, using e.g. WHO guidelines, are using HCQ in such a way as to practically guarantee mortality:
Simarly, the anti-viral drug Tamaflu only works for seasonal flu if taken within 48 hours of the first onset of symptoms.