How to put your opponent in zugzuwang
1. If there are still pieces on the board, restrict and/or pin them, so they cannot move (without serious loss)
2. Make sure that you have more pawn moves than your opponent until they hit a square from where they cannot advance any further.
can it still be achieved in the middlegame?
can it still be achieved in the middlegame?
Yes.
The most famous Zugzwang game was achieved in the middle-game, not the end-game.
Immortal Zugzwang Game - Wikipedia
How to put your opponent in zugzuwang