As a workaround you could try to use a third party software to bind W and S to mouse buttons. I used ATNSOFT key remapper a couple years back, it was easy to use and pretty sure it was free.
I don't even know how to ask you... I love your game...but there is one problem... I recently lost several fingers on my hand. After a certain amount of mastering and getting used to the new conditions of my position, I got somewhat used to the new WASD management. As in any shooter (or similar game using WASD) , I replaced the "back"(S) and "forward(W)" buttons on the mouse in the key settings, using its side buttons (mouse5 and mouse4) for the above movement. This saved me both mentally and physically! But in Zomboid there is no way to configure additional side mouse keys to link to the character's movement control :( I love your game. Help me stay in it by adding the possibility of more flexible control settings. From Russia with love your sincere fan...
