If you log into Roblox: Grow A Garden after the event is already live, you won't receive the Chicken Zombie. As such, the only way to currently get this pet is by trading.

This gardening game has taken Roblox by storm, and its upcoming event is sure to win over even more players. Roblox Players Can't Get Enough of Its Cozy Gardening Game (And It's About to Get Even ...