do you want them to move on a set path, or with some varying function?
either way shouldn't be too difficult. set points using the angle you want and order them to move to there.
If you don't like that then you can just have them move with some variation of a "knockback system" where the only ways they can move are vertically and horizontally.
if you want them to be player-controlled, then maybe give them a seperate ability to go each seperate direction with a pushback type movement mechanic. and if you want it to work automatically, you can just bump the unit vertically and horizontally (separately) untill it reaches the point it was ordered to go to.