The bid of (regular) Nil by both sides is unusual, but not unique. When two separate Nils are bid by the same team, it is called bidding a "twin" Nil. Both players must have most of the low cards in all suits (or voids) in order to prevent having one or both of twin Nils defeated by repeated low card leads. Obviously, any middle or high spade held by either Nilling partner will prove to be fatal.
As for both members of the same team bidding twin Double Nils, that is much rarer. Then again, if you are losing by a bushel of points, it must warm the hearts of your opponents if your twin Double Nils both make, and you rescue a lost game from the fire!
Imagine that! Raking in 400 points in one hand! Now there is a concept!
