is there any way to attack better with azir soldiers?

"most mechanically difficult champion on league"

Probably just practice and get used to how it works. I honestly can't give any tips, but I'd imagine there's no trick to actually get better at it other than practice.

When pushing minions, make sure to place the soldier where it will actually hit multiple minions (on one end of the line). This may mean that you have to wait for them to stop moving. If you aren't trying to push the wave, either position the soldiers so they only hit one (outside and not in line with the minions) or just use your own AA instead.

When attacking champions in lane, try to position the soldier in the enemies retreat path if possible. This will make it more likely for you to get off extra attacks. Also remember that there is a maximum range at which you can command an attack from your soldiers. It's pretty long, but you can have a soldier up that you cannot command attacks from.

The attacks can do damage slightly beyond the range you can click on. This means that you can sometimes damage a champion that you can't directly attack with the soldier by attacking a minion in line between the soldier and the enemy.