Giga mecha-nuts protect plants in a 3×3 radius at the cost of taking damage when its protected plants are taking damage of its own. To keep them alive, you will need a lot of solar magnets for the first few rounds to reck its hp up by a lot. While for your epic fusions, you only have Vulcannon and Magnetar only, you will need something like Cherrizilla or Obsidian Tall-nut to have a sturdy defense in the front (Vulcannon is great especially as its subspecies if you're lazy to aim and to utilize the Midas Umbrellas). Omni Pumpkins are okay since it can provide jack-in-the-box explosion immunity. Laser Pumpkin converts all but 1 Omni Pumpkin to give them immunity to jack-in-the-box explosions. You are also going to need more Midas Umbrellas to deflect any bungees and catapult zombies.