Drive, its like 5hrs max, probably less. From Detroit to Chicago will take u like 3.5-4hrs and Milwaukee is like 45mins-hr from Chicago.
If its an interview, just go the night b4, u might want to leave early to avoid Chicago's crazy traffic.
I think that'll be way better than flying, tickets might be kinda high.
I've done the Michigan(Detroit) to Chicago drive many times, its a straight shot down I-94, only bad thing is Chicago's traffic.