I think your ZW-L's would be a good choice for operating your MTH trains. (I'd love to have one of those myself. ) MTH will run on most Lionel transformers, at least the ones on their recommended list. The CW-80 is NOT on that list. Not sure of any others that are not recommended?
DCS would allow you to get the MOST out if your MTH PS2 or PS3 trains. I am not familiar with the MTH Z4000 or conventional operation, but the Z4000 MAY allow you to use more features than other transformers? I think they have some special stuff built I to them, but that may apply only to older engines?