hash a sha256 to have a 16bytes - hash

Question

hiiii ,
to reduce my sha256 length , i had made my own hash algorithme with my own hash table ( from a lot of exmple ), look at this code source :
struct // structure pour stoké les valeurs de h
{
int a;
} hh[8];
struct DAT // 256 valeur de 0-255 aléatoir
{
int a;
}
T[256]={256 value }
ch=x[0]; // save the first byte
for (j=0; j<8; j++)
{
// a basic hash function Xor
h=0;
for (i=0; i<len; i++)
{
h=T[h ^ x[i]].a;
//printf("%d ",h);
}
hh[j].a=h; // save the result
//printf("%d ",hh[j].a);
x[0]=x[0]+1; // increment the first element by one
}
x[0]=ch; // restor the first byte
// concatenate the 8 stored values of h
I remplace this function
wsprintf(hex,"%02X%02X%02X%02X%02X%02X%02X%02X",
hh[0].a, hh[1].a,
hh[2].a, hh[3].a,
hh[4].a, hh[5].a,
hh[6].a, hh[7].a);
by this loop of i
printf("\n = ");
for (i=0; i<8; i++)
{
hex[i]=hh[i].a;
printf("%02X",hex[i]);
}
now I wante to compress my hash to half length
printf("\n compressed hash= ");
for (i=0; i<4; i++)
{
lhex[k] = hh[i].a ^ hh[i+4].a;
printf("%02X",lhex[k]);
fprintf(fw,"%02X",lhex[k]);
k++;
}
Question:
is it correct if I use my own function ?
is it correct when i replace wsprint by a loop to concatenate the 8 stored value ?
for the last one I know its incorect because if I have 2 hache like this L+R and L'+R'(L & R for the leftand right bits) if my two hash hase L=R' and R=L' I will have the same compressed hash :( , have any idea for that ?
Thnx iOuss