Well, you lay out your table with columns Z, A, B, C, and D, and you start off with the values of ABCD as 0001, then 0010, then 0011, etc ... all the way up to 1111. The table will have ... what, 16 rows?
This is a fairly simple one, actually. You perform the AND operation with C and D, and the AND operation with B and the *reverse* of A. Then you take the two answers and you OR them together to get Z.