MYSTERY MEMORY LEAK: WHERE DID MY MEMORY GO?!

Yes you could have zombied processes and also because I see your page table is at about the same amount of memory usage and if you were to go to task manager and on the details tab I would be surprised if you saw any cmd or maybe a few but not the number of them that you are seeing in rammap. As such, the only way you are going to clear them is with a reboot or you could try in rammap under the Empty item at the dump and select empty working might work but guessing likely not in this scenario. Figuring out why or who the cause not very straight forward. 

First you could maybe look towards is this something in the first place that is generating cmd.exe to constantly be spun up that should be or isn't normal behavior. 

Could try running a procmon log and catch call for creation of cmd. Explorer.exe would be process actually creating the cmd process but you would look for how called for it before explorer created it. I would use a filter in procmon on Path contains cmd.exe. 

If cmd is being created constantly then could also usg msconfig from start-run and on services tab disable 3rd party services and reboot and check if still getting created and if not the can go thru process of elimination to determine which service it is. 

Hope that helps