1) Open TileZed
1.2) Select "Tools -> .pack files -> Pack Viewer"
2) Select "File -> Open .pack"
2.1) Go to \Steam\steamapps\common\ProjectZomboid\media\texturepacks
2.2) Choose "Tiles2x.pack"
2.3) Select "File -> Extract Images"
I recommend you to select "Each tile as separate image" [Warning: There are more than 9900 tiles!]
2.4) Press at "..."
2.5) Choose any empty folder
Modify tiles as you wish
3) Select "Tools -> .pack files -> create .pack file"
3.1) Select any folder where you want to save your texture pack
3.2) Name the texture pack as "Tiles2x"
3.3) Select "Output texture size" -> "2048x2048"
3.4) Press "+"
3.5) Choose the folder with your modified tiles
3.6) If you have chosen "Each tile as separate image" at 2.3) step, uncheck the box.
3.7) Press OK
3.8) BACKUP VANILLA TILE2X
3.9) Put the modified "Tiles2x.pack" into \Steam\steamapps\common\ProjectZomboid\media\texturepacks
Profit!
Russian Version [Русская Версия]