zsh vs bash, two redirection strategies

bash output

NONSWAPPED_OUT
nonswapped_err
tee out: NONSWAPPED_OUT
tee err: nonswapped_err

swapped_err
SWAPPED_OUT
tee out: SWAPPED_OUT
tee err: swapped_err

test

#! /usr/bin/env zsh
#! /usr/bin/env bash
# switching the above lines causes different results

# writes to both
the_cmd()
{
    echo ${1}_out;
    1>&2 echo ${1}_err;
}

# to visually distinguish stdout
to_upper()
{
    cat - | tr '[:lower:]' '[:upper:]'
}

rm -f stdout.txt
rm -f stderr.txt
{
    the_cmd nonswapped > >(tee stdout.txt ) 2> >(tee stderr.txt >&2 )
} | to_upper
echo -n 'tee out: ' ; cat stdout.txt | to_upper
echo -n 'tee err: ' ; cat stderr.txt 1>&2

echo

rm stdout.txt
rm stderr.txt
{
    { the_cmd swapped 3>&1 1>&2 2>&3- | tee stderr.txt; } 3>&1 1>&2 2>&3- | tee stdout.txt;
} | to_upper
echo -n 'tee out: ' ; cat stdout.txt | to_upper
echo -n 'tee err: ' ; cat stderr.txt 1>&2

zsh output

nonswapped_err
NONSWAPPED_OUT
tee out: NONSWAPPED_OUT
tee err: nonswapped_err

swapped_out
SWAPPED_OUT
tee out: SWAPPED_OUT
tee err: swapped_out