[Solved] Having trouble understanding output of line of code –

As for me then this

return 0*printf("%d",a[i]);

just a bad programming style.

At least it would be better to write instead

return ( printf("%d",a[i]), 0 );

not saying about

printf("%d",a[i]);
return 0;

Maybe this statement is found in a recursive function.

As for your question

Having trouble understanding output of line of code –

then this line outputs the value of the i-th element of the integral array a and exits the corresponding function.