hi, 
so im pretty new to CC4 and I've been battling this for about a week now and honestly i'm about to throw it in the bin..  i created some clothing in zbrush, uv'd remeshed it etc to the way i wanted it i imported it into CC4 as a cloth asset and transferred skin weights set to default option ( ive also tried setting all the bone scales to 0, and 1 ) but i can't seem to get rid of the annoying stretching on the clothing. at the armpits & groin area.

can someone please help me understand how to fix the skin weights 
I've added some screenshots of the stretching areas and the bone weights in the broken areas.

You can get cross-weighting like this when the clothing was modeled in A pose, or has really baggy sleaves. There is an option to specify that the arms mesh only weight to the arm bones. See here:
https://manual.reallusion.com/Character-Creator-4/Content/ENU/4.0/08_Creating_Custom_Assets/Arms-Layer-for-Transferring-Skin-Weight.htm

The post above is correct.  I will add to that to use the smooth brush where you have all those hard lines.  You want each color to fade into the next.  Looking at your images, I can see the hard line in the groin region is what's causing the stretching deformation there.

First, with mesh that dense as you have it there, I doubt you may do much in CC.
Mesh/Skin Weights Edit modes in CC are not optimized to work with such a large poly counts.

Lateral partitioning does not really work well either.
Starting with poor selection tool and ending with necessity to still workout stretched and deformed armpit areas after you spend all that time trying to select arms vertices.
Maybe you will have a better luck with it, but I never had.

Bottom line, you have to skin weight in T-Pose for hoodie and with legs moved apart for baggy pants.
The best, is to simulate your cloth in such a pose outside of CC and import into CC for skin weighting.

If you can't import baggy cloth in correct pose then you might get stuck.
Attempting to fix armpits stretching directly in Skin Weights is hard because Smooth Brush is extremely slow. I bet it would not move on your mesh at all.
Smooth Brush in Mesh Edit mode is a lot faster, that's why I would try to fix it in reverse. So try...

Here is a practical example for fixing hoodie in reverse mode, where I fixed the mesh in edit mode and then reskinned.
Still not sure it will work out for you because of your mesh density. You might have to take it to  third party apps such as Blender to do the fixing.



Routine for baggy pants is a bit different. It's better be imported with legs slightly apart to begin with...

thanks for the links and examples,

ill have a look and make some changes to my meshes hopefully get it working :) 


--Update -- 
so i got the top to work better, 



the legs are however still giving me issues, after following  4u2ges's example.
i smoothed out the skin weights on the bones, and the legs are stilling at 26k polys, so im thinking may need to try resculpt them

If you reduced poly count to 26K per object, then you could probably do everything in CC.
Three main conditions are still valid:

1. You must design/simulate baggy pants with characters legs slightly apart. I have attached an optimal pose.
You may take them apart slightly more, but not too much. Otherwise weights transfer would get messed up.

2. Before you transfer weights you have to smooth mesh between legs (groin and butts) so that the mesh is smooth and there is no crisscrossing between left and right.

3. When transferring weights make sure to use Lateral Partitioning and fix any left/right inconsistencies.
As I mentioned in video, Lateral Partitioning works fine for legs, though I still do not like it for arms.

After you transferred weights, Put it back to A-bind pose and try to smooth weights for legs and pelvis bones in groin and butt. At 26K weights smooth brush would still be slow, but workable.