The video toaster sets in the Video slot. There is no way it's a Zorro II card. But if you look at the specs for the video slot, there is a lot more there than video. In addition to all the video signals from the DB23, there is the parallel port data. That's how the Amiga controls the Toaster.
It's correct that the TBC cards sold for the Toaster just used the Amiga ISA slots for power. Those were controlled via the serial port. There's a header in the 2000 where the first card connected, and daisy chained to the rest. You could put the same card into a peecee of that time just as well. They usually came with software for both.