As Crazy Dave is in command of LEAF, and all plants within the city limits, Zomboss thought he could organize an army of zombies that will take over the world, and all the brainz that came with it. As new Zombie technology was born, the zombies began their Invasion of the world. This army was known as Z-tech, the army which was supposively above any other army. As they began their attack, Many armies tried to shut them down by destroying them at their source, Zomburbia. Zomboss saw this coming in the first place, so he preemptively made a special kind of force-field that would put Z-tech in charge of any machine that enters it's perimiters, even missles! So many troops from around the world were lost, and the world was checkmated.
When all seemed hopeless, A new kind of army arose, THE PLANT REPUBLIC! The Plant Republic was immune to that meddelsome force-field because their weaponry wasn't machine based, or electrical, they have composite materials such as wood, and lawn in it's stead. So how does their tanks and planes drive? The answer lies within Rose's Sorcery. Any plant can control a vehicle thanks to a magic motor in every one. So as Z-Tech realized that The Plant Republic was the only hurdle, they had to eliminate that army! But to Zomboss's surprise, Dave is NOT the leader of this new threat. Instead, it is a strategic young man who had the knack for plants, and knew each of their strengths and weaknesses, Nyan!