I agree with the last comment. But I would prefer loosening the center battery and lifting it up to guide the trackpad cable easily. This also makes it easier to reinsert it into the connector during reassembly.
NOT necessary to remove this speaker.
NOT truly necessary to remove either speaker.
Because it is attached to the battery with a tiny bit of tape near where the spudger is in the picture, this cable should probably be loosened. But it is NOT necessary to remove the speaker entirely.
This step is NOT really necessary. The trackpad can be removed with this cable still in place.