Sometimes when a unit you place is near combat, no matter what you do as Zeus they like to do their own thing. To fix that disable FSM. and the unit will obey your every order.
To help you can also set the unit behaviour to CARELESS. This will kinda guarantee your unit moves in straight line.A units behaviour set to COMBAT, and FSM disabled will go where you want but they might take the slow way there.
Remember when you disable FSM the units will ignore incoming threats, incoming fire, being hit and not engage enemies (unless very close)
You can disable FSM using the Change Abilities module of Achilles and you can change the behavior by double clicking on the units group icon.