I'm not quite sure how zithromax (z-pak) will work against SARS-CoV-2. Antibiotics work against bacteria, not viruses. SARS-CoV-2 is a virus. My best guess is that it is being used to combat opportunistic infections caused by bacteria that are taking advantage of an opportunity due to the altered microbiota and breached integumentary barriers that resulted from SARS-CoV-2. I just can't imagine that zithromax has much efficacy against SARS-CoV-2 itself.
Meanwhile, remdesivir appears to be a much more promising drug to combat this new coronavirus. Remdesivir is an antiviral that has shown great efficacy when used to combat the Ebola virus. In the lab it has been shown to disable RNA replication in other coronaviruses such as MERS and SARS-CoV. There are now five large clinical trials taking place and some of those results will start to become apparent in early April.
One of my larger customers, University Hospitals in Cleveland, is one of the clinical trial sites. For anyone interested
here is a non-scientific article about UH's involvement in the trial.