[Phalanx]

I bought "zombie flesh eaters" which I'd never seen, the other day.
There was some trailers on the dvd, including one for this film, and zombie holocaust (also not seen).
So, I watched them.
For some reason, the film I'd bought was previewed under "zombie"
and the other one, zombie holocaust, was under "doctor....?something?...medical deviant"?
What's with all the naming differences?

Also...I know I've seen sequels for "zombie", does that mean they're sequels to the one I have now?

One more thing...seems I quite like these gore filled 70's zombie stuff...any further suggestions for films like this?