From https://cassels.com/insights/the-cassels-conspectus-no-1-financial-blackout-periods/:

"Blackout periods are not a mandated requirement imposed by law or stock exchange policies but constitute an important preventative compliance measure widely adopted by public companies. The objective of blackout periods is to help reduce regulatory investigation risks and reputational risks associated with the appearance of improper trading by prohibiting it during periods when important disclosures, such as financial statements, are being prepared and finalized for public release."

The only restriction at law is against trading on insider information generally, which may arise within or outside of circumstances contemplated within an internal policy. Whether Zenith or RVX have internal policies pertaining to blackout periods, and if so, what they contain, may be a good question to ask at the AGM, or to Chris at IR.