Shaquille O'Neal is throwing shade at Dwight Howard again ... proving that a Lakers jersey won't protect DH from the wrath of the Diesel.

Shaq and Dwight have been going at it for years -- some people trace the feud back to a 2007 dance battle ... when a young Dwight tried to eat Shaq's metaphorical heart (don't worry, Shaq battled back and took his head).

Over the years, the shots continued ... with Dwight even trying to use Shaq's famous "Superman" moniker at one point. That didn't go over well with O'Neal.

So, when we saw Shaq at Papa John's in ATL -- where he was giving away free pizza to kids -- we had to ask how he felt about the Lakers signing D12 in the wake of Boogie Cousins getting injured.

"Who?!? I don't know him," Shaq cheekily told us ... trying to turn the focus back on the food.

Point is ... Shaq's a Lakers legend with his own statue on the side of the Staples Center -- so if Dwight wants to win back Lakers Nation, he's gotta figure out a way to win over Shaq, quickly.