The answer is that Ross Andru penciled most of a terrific-looking 15 page insert to be included in Swamp Thing, before going off into her own book. But for reasons sadly lost to history (meaning, for the life of me, I can no longer remember why), we never went ahead with the series.
The answer is that Ross Andru drew much of a visually impressive 15-page insert intended for inclusion in Swamp Thing, before switching to his own project. Unfortunately, the decision not to continue with the series has been lost to history.