Zirconia crowns are adjustable, especially if they have a layer of porcelain over the front and incisal edge. It is really important that you determine that shortening one is the best answer for your smile. And how you can tell is to take a sharpie black marker and just lightly color in the lower edge to where you think it looks best. Step back and look in the mirror. Is that length good for your smile or does it make your front teeth too short? If good, adjustment is all you need. If too short, you might consider redoing the shorter crown to make it longer. Once you know what to do, take a little alcohol on a cotton ball and gently rub off the black line. It will all come off - I promise! Best of luck to you.
