suppose A is conquered by B, he attacks B at ETA 3, at same tick and ETA he attacks C another free colony and suppose he has sent enf to win the battle in both cases.
will A conquer his conquerer and colony C?
It should. However sometimes (rarely) it will say C is already conquered, you can't conquer him. I tend to play it safe and attack C a tick after the attack on A lands, however most people do just attack on the same tick
Hope that helps.