How can I modify these?

the instruction lea loads the Effective Address of its operand

so after executing lea rcx, qword ptr ds:[xxxxxxx]

rcx will hold the address xxxxxxx

so if you are sure you need rcx to be 0 in that instruction simply wipe the address from that specific operand

that is make 48:8d05 xyzabcd as 48:8d0425 00000000

or assemble lea rax,qword ptr ds:[0]

keep in mind this requires one extra byte because of rip relative addressing 8d05 00000000 will address the next instruction in x64 and will destroy the ret opcode

having said that what you are trying to do simply doesnt make sense that instruction returns an address which will be acted upon returning 0 to process further will surely result in access violation down the line

assume the returned address holds a string whose length is checked further down what will happen if NULL address was passed to that function

these kind of construction often represent a switch case or jump table construct read about them

below is a samll poc that will generate code similar to your screenshot

#include <stdio.h>
char *a[] =  
{
    "Your Name","Our Name","Her Name","His Name","Their Name","That Name",
    "This Name","What Name","Why Name","Where Name","How Name","Whose Name",NULL
};
char *getname( int indx ) 
{
    switch(indx)
    {
        case 'a': return a[0];
        case 'b': return a[1];
        case 'c': return a[2];
        case 'd': return a[3];
        case 'e': return a[4];
        case 'f': return a[5];
        case 'g': return a[6];
        case 'h': return a[7];
        case 'i': return a[8];
        case 'j': return a[9];
        case 'k': return a[10];
        case 'l': return a[11];        
        default:  return "NoName";
    }
}
int main(int argc,char *argv[]) 
{
    if(argc !=2) return 0;
    printf("%sn" , getname(*argv[1]));
    return 0;
}