The zoom client installed from AUR (and also the one from flatpak) had two weird issues:

1. the window didn’t show up
2. the window is oversize and cannot be rescaled.

checked the terminal output (there’s no output) and the log file under $HOME/.zoom/log (nothing suspicious).

Solution

After few google searches, I found a workaround

vim $HOME/.config/zoomus.conf

autoScale=false

I reinstalled the zoom (restart also works) and it worked