Noisy (Knocking) Suspension
A common issue with Zafiras is faulty / damaged drop links. These are part of the suspension system and join other parts together for strength and stability. The go through a lot of stresses and can wear out, they have rubber bushes to absorb forces and reduce noise. When these fail in some way you'll hear the familiar knocking sound.
What to do:
To resolve this you can try replacing the bushes, or just go for new drop links entirely which is probably a better idea if you've already taken everything apart.