The Zone VI viewing filter can be very helpful if you have realistic expectations and know what it is actually supposed to do. It helps in determining whether you might want to use, for example, a yellow, green, or red filter to separate tones in the scene. In a shot of a green and red pepper side by side with color film there is a dramatic difference between the two visually, but in a black and white print they may look nearly identical, depending on the black and white film you choose. When you look at the scene through the Zone VI filter, it will help you approximate what a black and white print of that scene wil look like and whether a filter would produce the separation you are hoping for.
The Zone VI filter takes a little getting used to and will not perfectly render what every black and white film will produce, but could be worth trying out in terms of helping you visualize results.
Good luck with it if you do try it.
Doug Webb