Humanoid always falls when Unanchored?

I have a zombie which is anchored when spawned, but after 3 seconds it gets unanchored and just falls down. I want the zombie to instantly start walking when he gets unanchored. I am trying to make an animation, where a zombie comes up from the ground, like in the game Zombie Attack. This is the code I have now:

function SpawnZombie()
    local zombieTorso = script.Parent.HumanoidRootPart

    --zombieTorso.Anchored = true
    script.Parent.Torso.CanCollide = false
    script.Parent["Left Leg"].CanCollide = false
    script.Parent["Right Leg"].CanCollide = false

    for i = -5.5, 4.5 do
        zombieTorso.CFrame = CFrame.new(zombieTorso.Position.x, i, zombieTorso.Position.y)
        wait(0.1)
    end

    --zombieTorso.Anchored = false
    script.Parent.Torso.CanCollide = false
    script.Parent["Left Leg"].CanCollide = true
    script.Parent["Right Leg"].CanCollide = true

    zombie:MoveTo(Vector3.new(0, 0, 0))
end