I have an odd problem with zsh when switching between shells:

Option 1:
---------------
I start a Zsh shell, I then switch to tcsh with /bin/tcsh
and I then switch back to zsh with /bin/zsh

everything works well, e.g.
$ls
./  ../ file1 file1 file3


But, if I do:

Option 2:
---------------
I start a Zsh shell, I switch to tcsh with:
exec env -i HOME=/home/james TERM=xterm-256color DISPLAY=localhost:12.0
/bin/tcsh

and then back to zsh with /bin/zsh, then when I enter my subsequent
commands, the shell echoes the command and then the result,

e.g.

$ ls
2;ls --color=yes -aF1;ls./ ../ file1 file2 file3

In other words, zsh shows 2;COMMAND 1; and then the output without line
breaks, which is of course very different from what I was getting with
Option 1.

What can I do to diagnose the problem? Any pointers would be greatly
appreciated

Thanks,

James