I have a working theory demons speak a kind of drunken/slurred sounding version of Enochian, with human phrases that have similar meanings in several languages worked in.
Kind of like the hybrid “thieves languages” and other similar slang and patois languages in human cultures. I have some confirmation of that, but it was stuff from an evocation so I won’t expect anyone to take that on board as solid proof.
In that case, checking this page: https://web.archive.org/web/20180213200425/http://www.angelfire.com/empire/serpentis666/Letters.html
Z= they
ZACAM= I move you
ZACAR= move, move appear (so, ZA appears to relate to movement, travel, appearing/manifesting)
and
A= hast, in, on, of, with, the
AS= was
ASA= was
ASAGE= AS GE, was not
ASA-MOMARE= AS MOMAR, was (and shall be) crowned
ASAPATA= ASPT, before, in front of
So IF that’s correct, “ZAZAS” seems like a general summoning, “They are in (this world) and manifest” - a statement not unlike the statements of present tense and intended outcome combined that are used in spells and affirmations.
Just a theory but when you consider these spirits may exist outside time, telling them they will, are, and have appeared NOW by YOUR bidding makes sense.
I don’t have time to look up Nastananda but Ananda is (in Hinduism, Buddhism, and Jainism) extreme happiness, one of the highest states of being. Maybe it’s an inviation of enjoying being here that revokes the countless times humans have burned or damned demons to torment and flames, a kind of “Appear here through gates of joy”?
Maybe Nast is derived from nasty, a word we all know, and meant to remove any sanctimonious/religious vibration in Ananda… just shots in the dark there though. 
I say again, working theory only but the links between a couple of enns and the syllables and some of the words in that dictionary I linked are pretty strong.