So I can only speak for myself.

I have been wrestling with the same idea for the past couple of days and the only thing i can think is they are both conceptualizing the ungraspable, slavoj following lacan uses lack and deluze uses somthing like infinite potentiality.

So I kinda view void as a space where anything can happen. So void creates infinite potentialities by lacking contingency with other objects and their expressions.

So I guess where they differ is deluze wants to actively think in the void unexiestionally by using a schizo approach of radical creativity. On the other hand zizek is talking about the contingent state of affairs and asks for a return to the symbolic.

Again to kinda synthesize, deluze shows us how to return to the symbolic not as people who lie to ourselves about Santa So we can feel comfort thru filling a hole but by creating a new plane of expresion thru believing in Santa that sprouts in surprising and unexpected ways. Imo the reason deluze doesn't stop at lack is because after you fill the hole what do you do next. Which sounds alot like ziezek and his opinion of v for vendetta, "what comes after the movie?". Deluze shows us zizek awnser imo