zopen vim does not understand FilterWritePre

[runningppl]

It seems the zopen VIM does not understand FilterWritePre. ( https://vimdoc.sourceforge.net/htmldoc/autocmd.html#FilterWritePre )

To reproduce the problem:
1. create a file myvimrc as follows 
> cat myvimrc
au  FilterWritePre * if &diff | echo "____HELLO WORLD____"

2. vim -u myvimrc -d aaa.txt bbb.txt   # aaa.txt bbb.txt do not need to exist
=> OR <=
In your own .vimrc, insert the command at 1 and 'vim -d aaa.txt bbb.txt'

When the autocommand(au) runs successfully, HELLO WORLD is found [refer to the screen cap] But with zopen VIM, the output is not found

[MikeFultonDev]

@IgorTodorovskiIBM fyi