Yes, and no.
Yes, power wise, is electrically "compatible"
Physically- no, because Lionel used the "Fat pin" sized version of the power entry jack on Fastrack.
You need an adapter to go from fat pin to skinny pin sized coaxial jacks.
Again, Lionel Fastrack has a 5.5mm OD x 2.5mm ID https://ogrforum.com/...c/129252226560423354
The MTH Z brick (500,750, and 1000) used 5.5mm x 2.1mm
So you need an adapter to physically and electrically connect.
Search for "Power Adapter 5.5mm x 2.5mm Male Plug to 5.5mm x 2.1mm Female Jack"