Black Screen with UIViewControllerAnimatedTransitioning

You need remove mask layer once your are done with custom transition animations.

toViewController.view.layer.mask = nil

Please use this updated code:

class ZoomInCircleViewTransition: NSObject, UIViewControllerAnimatedTransitioning, UIViewControllerTransitioningDelegate {

var transitionContext: UIViewControllerContextTransitioning?

func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
    return 0.6
}

func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
    self.transitionContext = transitionContext

    guard let toViewController: UIViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey) else {
        return
    }

    guard let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey) else {            return
    }

    guard let fromViewTransitionFromView = fromViewController as? TransitionFromViewProtocol else {
        return
    }

    let imageViewSnapshot = fromViewTransitionFromView.getViewForTransition()

    let endFrame = CGRectMake(-CGRectGetWidth(toViewController.view.frame)/2, -CGRectGetHeight(toViewController.view.frame)/2, CGRectGetWidth(toViewController.view.frame)*2, CGRectGetHeight(toViewController.view.frame)*2)

    if let containerView = transitionContext.containerView(){
        containerView.addSubview(fromViewController.view)
        containerView.addSubview(toViewController.view)
        containerView.addSubview(imageViewSnapshot)
    }


    let maskPath = UIBezierPath(ovalInRect: imageViewSnapshot.frame)
    let maskLayer = CAShapeLayer()
    maskLayer.frame = toViewController.view.frame
    maskLayer.path = maskPath.CGPath
    toViewController.view.layer.mask = maskLayer

    let quadraticEndFrame = CGRect(x: endFrame.origin.x - (endFrame.height - endFrame.width)/2, y: endFrame.origin.y, width: endFrame.height, height: endFrame.height)
    let bigCirclePath = UIBezierPath(ovalInRect: quadraticEndFrame)

    let pathAnimation = CABasicAnimation(keyPath: "path")
    pathAnimation.delegate = self
    pathAnimation.fromValue = maskPath.CGPath
    pathAnimation.toValue = bigCirclePath
    pathAnimation.duration = transitionDuration(transitionContext)
    maskLayer.path = bigCirclePath.CGPath
    maskLayer.addAnimation(pathAnimation, forKey: "pathAnimation")


    let hideImageViewAnimation =  {
        imageViewSnapshot.alpha = 0.0
    }

    UIView.animateWithDuration(0.2, delay: 0.0, options: UIViewAnimationOptions.CurveLinear, animations: hideImageViewAnimation) { (completed) -> Void in
    }

    let scaleImageViewAnimation = {
        imageViewSnapshot.frame = quadraticEndFrame
    }
    UIView.animateWithDuration(transitionDuration(transitionContext), delay: 0.0, options: UIViewAnimationOptions.CurveLinear, animations: scaleImageViewAnimation) { (completed) -> Void in
        // After the complete animations hav endet
        imageViewSnapshot.removeFromSuperview()
        toViewController.view.layer.mask = nil
    }
}

override func animationDidStop(anim: CAAnimation, finished flag: Bool) {
    if let transitionContext = self.transitionContext {
        transitionContext.completeTransition(!transitionContext.transitionWasCancelled())
    }
}

// MARK: UIViewControllerTransitioningDelegate protocol methods

// return the animataor when presenting a viewcontroller
func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    return self
}

// return the animator used when dismissing from a viewcontroller
func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    return self
}

}