Hopefully your wife is supportive in your rules and the punishment you want to deal out to the 2 girls or you will be in the same boat as myself. Trying to keep order with rules and punishments are just causing your wife to stand behind her daughters and actually approve the behavior or disapprove of the punishment you want to deal out as your wife isn't doing anything.
Take away cellphones, no TV, grounded for a month ect should help keep them out of the external bad influences so this can be sorted out but if your wife doesn't support you with this then you are on the divorce path.
I have a 10 year old step daughter who is luckily not on that path yet but has 0 respect for her mom or myself, if she has to be punished I have to do it and what ever I do my wife will turn against me and take her daughters side (even when her daughter hits my wife, "it's only a little bump"). My 14 year old stepson has less problems but treats his mom like a piece of crap, slips school, does really bad at school and I constantly have to speak to him about this and when I again do or try to punish him by taking away his cellphone ect I get blasted by my wife.
They never try this at their father as he doesn't take the crap and he and his new wife are together in rules and punishment.
This is also rubbing off on our 3 year old daughter as she sees how the other kids are allowed to speak to their parents and then sees her mother swear and shout at her father. Now this happens 3-5 times a WEEK. We are on the verge of divorce because of this.
So hopefully you can get you wife in the same boat as you and stand as one or there is no hope left.