Zwischenzugs - Keep Your Eyes Open

Hi Chess Friends,

Yesterday, I played a few online blitz games and the final two of them were decided by the same sort of tactic. In each game one, or both players, missed a zwischenzug, an in between move. The idea of in between moves is simple. It's easy to get caught up in an automatic looking series of exchanges, but if you don't look to the rest of the board, you may miss something important.

Here's a good example of white winning a pawn with an in between move. You don't have to take the queen on d4 immediately, even if black has just taken your queen.

Yesterday, in the following position I had just played a serious blunder, putting my knight on e5. Can you see how white can win material? Please answer in the comments.

I lucked out in that game, as my opponent played the meek fxe3, and I won quickly. 

I had learned my lesson in the next game, as my GM opponent missed a Zwischenzug after 14...Nxe3. See if you can find it.

The full game is below.

I hope you enjoyed the puzzles. If you have any fun examples of a Zwischenzug, please post in the comments.