Thick Subtool Retopology Problem

[mmchk]

Hi 3d people

I made hi-res model of soldier with backpack, bullet proof vest and T-shirt. The T-shirt was made as a subtool by extract function. Because T-shirt is a piece of cloth, its pretty near to his chest. When i was going to retopology it, i merged all subtools and did my new lowres topology. But when i hit project button, it returned mess. Z brush cant decide correctly which mesh is on the top so sometimes it project t-shirt and sometimes his chest - it look like Picaso. So how can i retopology it correctly unles i delete pieces of chest under t-shirt?

Thank You !