How hard is it to remove 6 zirconia crowns and will it be likely a tooth would break during the process ?

Recently got 6 zirconia crowns on front 6 teeth. 5 of these teeth hAve had root canals years back. The dentist commented that my teeth were very dark colored. Is this why he chose the zirconia? I was under the impression I was going to have all porcelain. It's only been a short while but I'm not happy with them. Too white and not natural looking. Would it be too traumatic to my root canal teeth or the one live tooth I have left of the 6. I've read it can take hours just to get one drilled off