How do restrict pan gesture recognizers to when a pinch gesture is occurring?

How do you only accept pan gestures when the user is in the process of a pinch gesture? In other words, I'd like to avoid delivering one finger pan gestures.

@IBAction func pinchPiece(_ pinchGestureRecognizer: UIPinchGestureRecognizer) {
    guard pinchGestureRecognizer.state == .began || pinchGestureRecognizer.state == .changed,
          let piece = pinchGestureRecognizer.view else {
            // After pinch releases, zoom back out.
            if pinchGestureRecognizer.state == .ended {
              UIView.animate(withDuration: 0.3, animations: {
                pinchGestureRecognizer.view?.transform = CGAffineTransform.identity
              })
            }
            return
    }
    adjustAnchor(for: pinchGestureRecognizer)
    
    let scale = pinchGestureRecognizer.scale
    piece.transform = piece.transform.scaledBy(x: scale, y: scale)
    pinchGestureRecognizer.scale = 1 // Clear scale so that it is the right delta next time.
}

@IBAction func panPiece(_ panGestureRecognizer: UIPanGestureRecognizer) {
    guard panGestureRecognizer.state == .began || panGestureRecognizer.state == .changed,
          let piece = panGestureRecognizer.view else {
        return
    }
    let translation = panGestureRecognizer.translation(in: piece.superview)
    piece.center = CGPoint(x: piece.center.x + translation.x, y: piece.center.y + translation.y)
    panGestureRecognizer.setTranslation(.zero, in: piece.superview)
}

public func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,
                            shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    true
}