In Z the computer player does not play a pre-set strategy but reacts in real-time to the decisions that the player makes. Therefore it is not possible to define a sequence of orders for each level which will guarantee winning a battle. However there is a basic strategy that should be employed which will establish a good foothold from which the player can win a level.
All the one player levels are designed so that the two halves of the battlefield mirror each other. This means that both the computer and the player each have the same resources available to them in their half of the map. It therefore follows that as long as you have control of your half of the map you will be level with the computer. Managing to capture one more territory will give the player a slight advantage both in resources and the time taken to manufacture units in the buildings owned. Understanding this basic principle is fundamental to developing a winning strategy in any of the battlefields.
At the start of the game there are some basic moves that you should make. Give orders for your units to capture the territories in your half of the map, and any uncaptured hardware contained within it. Whilst your units are carrying out these orders, use the time to set up any captured buildings to make the required units. Once these territories have been captured, you should locate the connecting roads between your territories and the computer's. Units must be moved up to this front-line to defend against the computer trying to enter territories which you control.
As units are manufactured you should bring them up to support this defence. Always scan the map to see what the computer is doing to react to any planned attacks. Find territories which the computer has either left undefended or which have little defence. Attack these territories only when you have units which exceed the power of the computer's defending units.
Do not believe the battle is over if you manage to gain the territory advantage over the computer. He will fight hard to regain control of any lost territories. Of course this is also true for the human player. Losing one or even two of your territories to the computer does not mean the end of the battle. Playing hard and recognising those territories which are easily re-captured will get you back into the game.