Overwriting textures of another mod works with items but does not with armor

[Witchkings]

Hello there! I'm making an addon/connector between Epic Knights and TerraFirmaCraft, and I've already done initial release but now while working on retexturing Epic Knights' armor to match with TFC artstyle I've encountered a problem which is in the title. I tried to replace a vanilla armor with my texture and it worked. I tried to replace items from Epic Knights and it worked. I tried to replace armor in both TerraFirmaCraft and Epic Knights and it did not work. Any help woukd be appreciated. 

Btw resourcepack works and replaces armor just fine. But I don't want to use it. 

 

https://imgur.com/a/Hvd9Faq here are all the screenshots

[Xoroshio]

Mmmm this part of modding is not my strong part, and all the advice I can give is that retexturing the armour is imposible, or that your names/directories are wrong

[Witchkings]

Retexturing is absolutely possible as vanilla armor retextures just fine and names&directories are also fine because resourcepack works fine but as I merge it into mod files it doesn't
may I ask you to check it out yourself?