It would have been "running on a Power PC that is emulating a 68K that is emulating a Z8000". We used to joke about that.
But in fact they changed from "running on a 68K that is emulating a Z8000" to "running on a Power PC that is emulating a Z8000".
They ported their Z8K emulator from 68K to PPC which wasn't super hard. When the PPC was designed it was planned as an upgrade path from 68K series (remember it was a JV between Apple, Motorola and IBM; the first two, at least, had vested interests in making that transition as easy as possible).
This whole stack of emulation sounds crazy but given their needs, it wasn't.
But in fact they changed from "running on a 68K that is emulating a Z8000" to "running on a Power PC that is emulating a Z8000".
They ported their Z8K emulator from 68K to PPC which wasn't super hard. When the PPC was designed it was planned as an upgrade path from 68K series (remember it was a JV between Apple, Motorola and IBM; the first two, at least, had vested interests in making that transition as easy as possible).
This whole stack of emulation sounds crazy but given their needs, it wasn't.