.zprofile not used correctly after High Sierra

I am a Unix user and have been using zsh for more than 20 years. I have been using zsh as my login shell for many years on macOS High Sierra. I use only ~/.zprofile and for sharing what is relevant to be common, with /bin/sh and /bin/bash it calls explicitely ~/.profile. I don't use any other shell initialization file outside of: ~/.zprofile ~/.profile Recently I made the switch to Big Sur. And I discovered a problem which didn't occur before and which doesn't occur on any Unix I work on: inside Terminal and xterm my ~/.zprofile is not correctly read. Since I didn't pass on Catalina ( too many problems ) I cannot verify if the problem started with Catalina or Big Sur. If I load it explicitely: . ~/.zprofile it is read without any error. Most notably I see it at the setting of PS1 which is the correct one I see on all other systems I am working on. I didn't modify either /etc/zprofile or /etc/zshrc. Here are my very basics shell initialization files: --- # ~/.zprofile #! /bin/zsh . ${HOME}/.profile PS1="### %B%T %m%b:%32<...<%/ %# " export PS1 PS2="# " export PS2 HISTFILE=~/.zsh_history export HISTFILE HISTSIZE=1024 export HISTSIZE VISUAL=vi export VISUAL tty -s && stty -istrip --- # ~/.profile #!/bin/sh CDPATH=.:~/Links export CDPATH PATH=/opt/local/bin:/opt/local/sbin:/bin:/usr/bin:/sbin:/usr/sbin:/opt/X11/bin:/opt/bin export PATH MANPATH=/opt/local/share/man:/usr/share/man:/opt/X11/share/man:/opt/man export MANPATH LANG=en_US.UTF-8 export LANG BC_ENV_ARGS="${HOME}/.bcrc" export BC_ENV_ARGS