！
Why the hell aren't you running for it?!
Literal
Why-the-hell flee-[negative-ねえ] [emph-んだ]!
なんだって is a rough, demanding 'why the hell / what the hell' interrogative. ずらかる is colloquial slang for 'to flee / skedaddle'; the negative ずらからない becomes ずらからねえ through the rough-masculine ない → ねえ contraction. The final んだ is the assertive / explanatory, rounding off the tone into a belligerent demand.