Why would you do it from a cellphone. ?
Zoom client is better, and for that matter any video meeting software, works the best at the client vs the browser.
Whatever the difficulties, everything will be on hold, until you can get back online with your respective presiding judge to take the oath.
If ZOOM goes, down, there is nothing you can do about it. If you internet is choppy, then you have to hope , on this day it stay stable for sometime. I am sure, you have to deal with any issues as they come.
As long as your net connection is fine at your end, you should be OK.