First time posting due to the dedication of other posters more...

First time posting due to the dedication of other posters more experienced abd informed than myself! But found an article possibly pertinent to your question. Best one I could find with a search of failed wildcat drilling in Zimbabwe and of North neighbouring countries Zambia and Mozambique, .
https://www.reuters.com/article/zimbabwe-oil-idUKL8N1XD0TE

Only speculating because I wasn't around IVZ then, but it appears more as a confirmation of no oil/gas for market disclosure purposes to the ASX, it was a prospective/potential resource and Invictus may have been covering for exuberant Zimbabwean media spillage, who would understandably be a bit loose with terms. There doesn't seem to be a failure as the 'The Top 5 Natural Gas Wildcats of 2021' article claims, as there was no drilling that took place to confirm a working petroleum system/discovery in 2018.

There may be a better answer but the article claiming a previous failure appears pretty irresponsibly loose and unsubstantiated as a final remark. From what I could personally recover at least.