[quote=@Little Bird]
Logistically speaking

Zac would likely be more concerned about getting himself and others to the ship. Anyone going with him would only fight to the extent that it gets them on board. 

Anyome getting off world by other means will be left fighting. 
[/quote]

That's basically what the idea was, that the two were going to hold off Darkside while everyone got on the ship. Anyone not getting on the ship of course can do whatever they want. 

The way I saw it was basically, Darkside is ahead, the ship is behind, so pretty much everyone is capable of just hopping on the ship, and will only fight if they choose to do so.