It is based on the zombie in Plants vs. Zombies 2 with the same name and appearance. However, it is controlled by an Imp Commander, has nothing on the sail, and has no Imp tied to the ship. It also gained a new laser attack.
Its description is a reference to its Plants vs. Zombies 2 ability where it floods the field with Pirate Imps.
Statistics
Class: Sneaky
Tribes: Pirate Science Zombie
Traits: Amphibious, Strikethrough
Ability: When played: Make two other random Pirates in random lanes.
Set - Rarity: Premium - Legendary
Card description
Deploying Pirates here, there and everywhere.
Update history
Update 1.2.11
▲ Strength change: 5 → 6
▲ Health change: 3 → 6
▲ Brain cost change: 9 → 8
▲ Trait added: Strikethrough
Ability change: When played: Make 1/1 Swabbies with Amphibious in every lane. All pirates get +2/+2. → When played: Make two other random pirates in random lanes.
Description change: Was originally Swabbies here, there and everywhere.
It is best to play this on the aquatic lane as it can trouble your opponent and grant it immunity to some powerful plants and instant-kill tricks like Super-Phat Beets and Lawnmower. Otherwise, if you play Zombot Plank Walker on any other lane, it may make one of the two pirates on the aquatic lane, which can be either a Swabbie, an Unthawed Viking, or the Zombot Aerostatic Gondola.
For extra information, here is the list of pirates Zombot Plank Walker can make:
If you want to wreak even more havoc, use this with either Swashbuckler Zombie as he will boost Zombot Plank Walker every time it attacks due to its Strikethrough trait, or Mixed-Up Gravedigger to reactivate its ability, as well as taking your opponent by surprise as they are unable to know what lane it will emerge out of. Also, while Captain Flameface has no effect on this zombie due to it already having the Strikethrough trait, he can still be used to support the other pirate zombies Zombot Plank Walker makes.
As for synergies with zombies in other classes go, Gadget Scientist can make it do some devastating bonus attacks due to its science tribe if used with Super Brainz/Huge-Gigantacus. Unlife of the Party will gain +3/+3 for Impfinity, although Zombot Plank Walker is often too expensive for Impfinity to remotely sustain when he is better off rushing.
Against
Zombot Plank Walker is very dangerous. Its strikethrough trait means you can't hide behind plants and it packs a serious punch. To lower or avoid the damage done, use Water Balloons or Weed Whack to lower Zombot Plank Walker's stats, or Freeze it to get some time. But for most, try to use instant-kill cards like Squash or Doom-Shroom, which can also help with some pirates made by it as well in case of the latter.
Although most likely, if the two random pirates made is at least a Shieldcrusher Viking, you will want to destroy that first. Otherwise, you may not block any attacks at all.
Unless you need to stall or to secure a victory, do not Bounce this zombie, as your opponent will very likely replay it, using any remaining available space to potentially make stronger pirates.
Gallery
Plants vs. Zombies Wiki has a gallery for Zombot Plank Walker.
The zombie controlling the machine is an Imp Commander. However, the Imp Commander on Zombot Plank Walker sounds much different from the original.
There was a rare glitch where Zombot Plank Walker couldn't be destroyed by direct combat, as when Swashbuckler Zombie was on the field, he would boost Zombot Plank Walker before it could play its "When destroyed" animation.
This is one of the only zombie cards in the game along with Deep Sea Gargantuar, Cardboard Robot Zombie, Electrician, Hippity Hop Gargantuar, Team Mascot & Fishy Imp to have one of 3 possible sounds play when spawned. Out of these, it is the only Legendary card.
Sneaky class. It costs 8
to play and has 6
/6
. It has the Amphibious and 
Strikethrough traits, and its ability makes two random pirate zombies, excluding another Zombot Plank Walker, on random lanes excluding the lanes occupied by a zombie.
Freeze it to get some time. But for most, try to use instant-kill cards like Squash or Doom-Shroom, which can also help with some pirates made by it as well in case of the latter.
Brainy
Crazy
Hearty
Sneaky