I noticed something very odd the last time I invaded an AI civ. The city I was attacking already had a garisonned crossbowman and finished another crossbowman when its turn came. However, instead of being forced to move the 2nd crossbowman the AI attacked with BOTH crossbowmen from the city, with the 2nd crossbowman getting "kicked out" of the city to an adjacent tile when the AI's turn ended. The AI didn't need to move the 2nd crossbowman before it fired (and it would have entered ZOC too). This appears to be blatant cheating since the player cannot do this manuever.
Even if a human player wound up with 2 Chu-Ko-Nu on the same tile (which actually can move after one attack), the game would force him/her to "move stacked unit" before firing.
Even if a human player wound up with 2 Chu-Ko-Nu on the same tile (which actually can move after one attack), the game would force him/her to "move stacked unit" before firing.