Because Construct 3 supports Z elevation, zoom is implemented as moving the camera on the Z axis, and 3D rendering requires a far plane (i.e. a maximum draw distance). Consequently while you can zoom to any value, you cannot draw objects at an unlimited distance away from the camera; so if you rely on extremely large objects extremely far away, they may in fact disappear. However I think this is an extreme way to design a game and there are probably alternative ways of getting the same effect without using such extremes.