The reverse of encode→pack is unpack→decode. You have to remove "layers" in the opposite order that they've been applied, so you're doing it in the wrong order.

I don't see any trivial way of extracting the string before it's decoded, unfortunately.

sub extract_text {
   $_[0] =~ s/^((?:..)*)\0\0//s or die;
   return decode('UTF-16le', "$1");
}

my $first_name  = extract_text($bytes);
my $middle_name = extract_text($bytes);
my $last_name   = extract_text($bytes);
my ($x, $y)     = unpack('VV', substr($bytes, 0, 8, ''));
my $address     = extract_text($bytes);
my $zip_code    = extract_text($bytes);
my ($z)         = unpack('V', substr($bytes, 0, 4, ''));
[download]

my @fields = $bytes =~ /
   ^
   ((?:..)*)\0\0
   ((?:..)*)\0\0
   ((?:..)*)\0\0
   (.{4})
   (.{4})
   ((?:..)*)\0\0
   ((?:..)*)\0\0
   (.{4})
   \z
/sx or die;

$_ = decode('UTF-16le', $_) for @fields[0,1,2,5,6];
$_ = unpack('V', $_)        for @fields[3,4,7];
[download]