As far as I know, cameras do not work this way. You really do not need a camera to do a zoom in, just use scale.
Most people who are new to After Effects often attempt to create, as you say, huge comps without knowing the value of prerendering.
What bogiesan said. The whole workflow sounds crooked and unnecessary. And yes, cameras don't collapse transformations, only actual layers. AE will always use the camera of the parent comp. And yes, collapsing transformations affects how blending modes are calculated, which is by design.
Without seeing your timeline I can't tell for sure but I would think that the project would work if you were to move your camera to the main comp, collapse transformations on the 3D pre-comp and go from there. If there are lights in the 3D comps you need to bring them to the main comp also if you are going to use collapse transformations.
I can see no reason that a 3D comp with a camera would not show up just as it is in your main comp with CT turned off. With it off, the layer is just another 2D layer in the stack. If there is nothing in the frame then something else is wrong.
My pre-comp works fine, when I say nothing happens, I mean there is no camera movement on the main comp as in the precomp.
If I move the camera to the main comp, and lights, The pre-comp gets the movement I want, but doesn't get rid of the resolution size of the pre-comp.
But I think that shoul do the trick if I increase the size of the precomp.
Thank you guys for all the help
Show me the timeline of the main comp and the pre-comp. If there's movement in the pre-comp then there has to be movement in the main comp. Just dropping a comp with a camera in another comp will not stop the action. A camera in the main comp has no effect on 3D layers or animation in a nested pre-comp unless you turn on Collapse transformations. If you have a camera in the Main comp and a camera in the pre-comp and you collapse transformations then the camera in the pre-comp and any lights in the pre-comp will be ignored.
Show us the comp and / or a flow chart.