In Figure 4.5 (Hack instruction set), if you examine it carefully, you can find that the "cccccc" corresponds to the 6 input ports "zx nx zy ny f no" of the ALU exactly, that is, instruction[11] is connected to "zx" ..., this observation should greatly simplify your implementation of nand2tetris/projects/5/CPU.hdl
In Figure 4.5 (Hack instruction set), if you examine it carefully, you can find that the "cccccc" corresponds to the 6 input ports "zx nx zy ny f no" of the ALU exactly, that is, instruction[11] is connected to "zx" ..., this observation should greatly simplify your implementation of nand2tetris/projects/5/CPU.hdl