Answer : $XY + ZY'$
To Cover, All the Four 1's, We can make Two Subcubes of Size 4.
One Subcube will be made of all the cells of ROW-2 and will cover the minterms $5$ and $9$
Other Subcube will be made of the Cells corresponding to minterms $6,7,14,15$ and will cover the minterms $6,15$