Zsh Bash difference

gistfile1.txt

$ cat /tmp/tmp
1
2
10
9


Bash:
D is array

bash-3.2$ D=`cat tmp`
bash-3.2$ for i in $D; do echo "x$i"; done
x1
x2
x10
x9

Zsh:
D is not array

$ D=`cat tmp`
$ for i in $D
do
echo "x$i"
done
x1
2
10
9

Zsh correct way:

$ for i in `cat tmp`
do
echo "x$i"
done
x1
x2
x10
x9

Zsh correct way 2:

$ Z=("${(@f)$(cat tmp)}")
$ for i in $Z
do
echo "x$i"
done
x1
x2
x10
x9