RLA format with MR

I need to render images with RLA format in order to take some depth effects in After Effects(depth matte and 3D fog).
I tried render, but rendered images that be in images folder are rla images and iff images.
Rla images have only color channel and iff images have only Z channel.
There is no trouble if I can combine these channel into one image format using photoshop or something, but I couldn't figure out the way.
Dose anyone has idea?

thanks