In order to buy all the shares the shareholders have to approve. In order to buy 50% of the company AFTER a capital injection is something that is much easier to obtain approval for (shareholders still have plenty of upside).
As for thinking that ZED will change its mind because "its investment is already falling" - well, you must consider these people to be complete idiots.
After a long due diligence Zed has decided to put £34m of its money to work. It will not change its mind based on £100k worth of shares being sold by who knows who.