I used the contact feature to ask Zwift Support about the Southern Hemisphere Zwift National Championships and it turns out that these events may very well not take place this year. See their reply below:
" Hi Charles,
Thanks for waiting!
I’m sorry it took a while to get an update. I was able to find out the person who had organized last year’s Southern Hemisphere Zwift National Championships is no longer with us, but we’re currently talking about the event right now. We don’t have current plans on running the Southern Hemisphere Zwift National Championships this year, but we have been discussing it. I’d recommend keeping an eye out on our Facebook page and our Community News Page for announcements within the next month, but if we don’t hold the event this year, we are interested in bringing it back next year. I’m sorry of that isn’t the best news, but if you’d like to check back in with us later, please don’t hesitate. We’re always happy to help!