Most likely you are using the zerostat incorrectly. There's no shame in that. Zapping an LP inside its wrapper or sleeve, whether paper or whatever, is never going to work. One reason your LP may stick to your felt mat is that felt itself is a good donor of negative ions to vinyl. But also, if you remove static charge from the surface of an LP with the LP held in the air OFF the platter while you zap it (the only way it works according to my observation), that takes care of the side you play only. The bottom side that goes against the mat will still be charged up to begin with. The Shure Corporation published a long paper on static charge many decades ago in which they showed that charge migrates from one side of the LP to the other, after you treat one side. Finally, when you are using the zerostat, with the LP in your other hand, pull the trigger all the way back with the gun held away from the LP. Then start with the gun near to the LP and very slowly pull it away while very slowly releasing the trigger, ideally so slowly that there are no "clicking" sounds.