There are, of course, a lot of explanations about what happened here and what this story means.
Shaloh (Torah Shebichsav, Tetzaveh) states that Rabbah brought R. Zeira to a level of Divine understanding, and with that divestment from his physical body, beyond his capabilities. As for the term "slaughtered" (שחיטה), he compares it to the phrase וישחטם במדבר in Num. 14:16 - the Jews who died in the desert didn't have their throats cut, they simply died a natural death.
The Lubavitcher Rebbe zt"l (in Likkutei Sichos, vol. 31, pp. 180ff) builds further on this, citing another statement from Shaloh (Shaar HaOsiyos) that with Torah scholars, drinking wine can go hand in hand with the revelation of deep Torah secrets. This, then, he says, is what happened with Rabbah and R. Zeira: they did indeed drink wine at their Purim feast, but more to the point is that Rabbah (whose very name - which literally means "great" - signifies his greater capacities) brought R. Zeira ("small") to such a level of ecstasy that his soul left him. (The Rebbe compares this to the deaths of Nadav and Avihu, which on the one hand is associated with their having drunk wine (Rashi to Lev. 10:2) and on the other hand is viewed as a sign of their greatness (Rashi ibid. v. 3, and Ohr Hachaim ibid. 16:1).
He then goes on to say that this is hinted at by the term שחיטה, for אין ושחט אלא ומשך (Chullin 30b) - shechitah means to "draw out" and elevate.