They can't increase this bid because it is "final", and even if...

They can't increase this bid because it is "final", and even if they got around that problem, they would have to pay the higher price to everyone who has accepted the offer.

So if they want to pay more, they can wait six months and then make a higher bid then, and then they only have to pay the holdouts and not the people who accepted the original bid. Look at ANE for example.

ZFX don't particularly need 100% right now. Companies often need to get 100% in order to directly access the cashflow of the company being taken over, or to have complete freedom to restructure its operations. ZFX doesn't need to do either of those things right away.