Electrical – Verilog Can’t resolve multiple constant drivers for net

I've searched for this on google but the answers are not clear to me. Act like I am very stupid please, as I am a freshmen ECE major. My lab wants to me to use Verilog to program a DE0 to display the numbers 0-9 on its displays depending on what switches we flip. We were tasked to to program it in Behavioral, Dataflow, and Structural styles. I have compiled and succesfully programmed the board in Behavioral and Dataflow style. My struggle is with the Structural. I am getting the following errors upon compilation.

Error (10028): Can't resolve multiple constant drivers for net "W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z" at Lab_3_b_structural.v(181)

Error (10028): Can't resolve multiple constant drivers for net 
"W_OR_X_OR_Y_OR_NOT_Z" at Lab_3_b_structural.v(176)

Error (10029): Constant driver at Lab_3_b_structural.v(142)

Error (10029): Constant driver at Lab_3_b_structural.v(157)

Error (12152): Can't elaborate user hierarchy "structural:h0"

Error (293001): Quartus II Full Compilation was unsuccessful. 7 errors, 10 warnings

Error: Quartus II 64-Bit Analysis & Synthesis was unsuccessful. 5 errors, 10 warnings

Error: Peak virtual memory: 453 megabytes
Error: Processing ended: Sat Oct 08 17:13:54 2016
Error: Elapsed time: 00:00:01
Error: Total CPU time (on all processors): 00:00:00
Error: Peak virtual memory: 453 megabytes
Error: Processing ended: Sat Oct 08 17:13:54 2016
Error: Elapsed time: 00:00:01
Error: Total CPU time (on all processors): 00:00:00

/* In this lab we are using Verilog to create the seven segment display on the DE0. 
We had to perform the lab using behavioral, dataflow, and structural. So, three tests */

module Lab_3_b_structural(SW, HEX0, HEX1, HEX2);

    input [9:0] SW;

    output [6:0] HEX0, HEX1, HEX2;

    wire [6:0] hex0, hex1, hex2;
    //DE0 is common anode
    assign HEX0 = ~hex0;
    assign HEX1 = ~hex1;
    assign HEX2 = ~hex2;

    structural h0 (SW[3:0], hex0);
    structural h1 (SW[7:4], hex1);
    structural h2 ({2'b00,SW[9:8]}, hex2);
endmodule 

module structural (bcd, hex);

    input [3:0] bcd; //WXYZ

    output [6:0] hex; //ABCDEFG

    wire W,X,Y,Z;
    assign W = bcd[3];
    assign X = bcd[2];
    assign Y = bcd[1];
    assign Z = bcd[0];

    //NOTS (Used By all Segments)
    wire W_NOT;
    wire X_NOT;
    wire Y_NOT;
    wire Z_NOT;
    not not1 (W_NOT, W);
    not not2 (X_NOT, X);
    not not3 (Y_NOT, Y);
    not not4 (Z_NOT, Z);


    //A =(W|X|Y|~Z)&(W|~X|Y|Z)
    wire W_OR_X_OR_Y_NOT_Z; 
    wire W_OR_NOT_X_OR_Y_OR_Z;

    or or1A (W_OR_X_OR_Y_NOT_Z, 
    W,
    X,
    Y,
    Z_NOT);
    or or2A (W_OR_NOT_X_OR_Y_OR_Z, 
    W, 
    NOT_X,
    Y, 
    Z);
    and FinalA (hex[0], 
    W_OR_NOT_X_OR_Y_OR_Z, 
    W_OR_X_OR_Y_NOT_Z);

    //B = (W|~X|Y|~Z)&(W|~X|~Y|Z)
    wire W_OR_NOT_X_OR_Y_OR_NOT_Z;
    wire W_OR_NOT_X_OR_NOT_Y_OR_Z;

    or or1B (W_OR_NOT_X_OR_Y_OR_NOT_Z, 
    W, 
    NOT_X,
    Y, 
    NOT_Z);
    or or2B (W_OR_NOT_X_OR_NOT_Y_OR_Z, 
    W,
    NOT_X,
    NOT_Y,
    Z);
    and FinalB (hex[1],
    W_OR_NOT_X_OR_Y_OR_NOT_Z,
    W_OR_NOT_X_OR_NOT_Y_OR_Z);

    //C = (W|X|~Y|Z)
    wire W_OR_X_OR_NOT_Y_OR_Z;

    or FinalC (hex[2], W_OR_X_OR_NOT_Y_OR_Z);

    //D = (~X&Y)|(~X&~Z)|(X&~Y&Z)|(Y&~Z)|W
    wire NOT_X_AND_Y;
    wire NOT_X_AND_NOT_Z;
    wire X_AND_NOT_Y_AND_Z;

    and and1D (NOT_X_AND_Y, 
    NOT_X, 
    Y);
    and and2D (NOT_X_AND_NOT_Z,
    NOT_X, 
    NOT_Z);
    and and3D (X_AND_NOT_Y_AND_Z,
    X,
    NOT_Y,
    Z);
    or finalD (hex[3], 
    NOT_X_AND_Y, 
    NOT_X_AND_NOT_Z, 
    X_AND_NOT_Y_AND_Z,
    W);

    //E = (~W&~X&~Y&~Z)|~W&~X&Y&~Z)|(~W&X&Y&~Z)|(W&~X&~Y&~Z)
    wire NOT_W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z;
    wire NOT_W_AND_NOT_X_AND_Y_AND_NOT_Z;
    wire NOT_W_AND_X_AND_Y_AND_NOT_Z;
    wire W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z;

    and and1E (NOT_W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z, 
    NOT_W,
    NOT_X, 
    NOT_Y,
    NOT_Z);
    and and2E (NOT_W_AND_NOT_X_AND_Y_AND_NOT_Z,
    NOT_W,
    NOT_X,
    Y, 
    NOT_Z);
    and and3E (NOT_W_AND_X_AND_Y_AND_NOT_Z, 
    NOT_W,
    X, 
    Y, 
    NOT_Z);
    and and4E (W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z, 
    W, 
    NOT_X,
    NOT_Y,
    NOT_Z);
    or finalE (hex[4], 
    NOT_W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z,
    NOT_W_AND_NOT_X_AND_Y_AND_NOT_Z,
    NOT_W_AND_X_AND_Y_AND_NOT_Z,
    W_AND_NOT_X_AND_NOT_Y_AND_NOT_Z);

    //F = (W|X|Y|~Z)&(W|X|~Y|Z)&(W|X|~Y|~Z)&(W|~X|~Y|~Z)
    wire W_OR_X_OR_Y_OR_NOT_Z;
    wire W_OR_X_OR_NOT_Y_OR_NOT_Z;
    wire W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z;

    or or1F (W_OR_X_OR_Y_OR_NOT_Z, 
    W, 
    X, 
    Y,
    NOT_Z);
    or or2F (W_OR_X_OR_NOT_Y_OR_Z, 
    W, 
    X, 
    NOT_Y,
    Z);
    or or3F (W_OR_X_OR_NOT_Y_OR_NOT_Z, 
    W, 
    X, 
    NOT_Y,
    NOT_Z);
    or or4F (W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z, 
    W, 
    NOT_X,
    NOT_Y,
    NOT_Z);
    and finalF (hex[5],
    W_OR_X_OR_Y_OR_NOT_Z,
    W_OR_X_OR_NOT_Y_OR_Z,
    W_OR_X_OR_NOT_Y_OR_NOT_Z,
    W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z);

    //G = (W|X|Y|Z)&(W|X|Y|~Z)&(W|~X|~Y|~Z)
    wire W_OR_X_OR_Y_OR_Z;

    or or1G (W_OR_X_OR_Y_OR_Z,
    W, 
    X,
    Y, 
    Z);
    or or2G (W_OR_X_OR_Y_OR_NOT_Z,
    W,
    X,
    Y,
    NOT_Z);
    or or3G (W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z,
    W, 
    NOT_X, 
    NOT_Y,
    NOT_Z);
    and finalG (hex[6],
    W_OR_X_OR_Y_OR_Z,
    W_OR_X_OR_Y_OR_NOT_Z,
    W_OR_NOT_X_OR_NOT_Y_OR_NOT_Z);
endmodule