ZSH started printed env on startup
I suggest you gather some more information.  For each of the login scripts (/etc/zshenv, /etc/zprofile, /etc/zshrc, /etc/zlogin, .zshenv, .zprofile, .zshrc, .zlogin), add a line at the beginning that prints to stdout something like ".zshenv starts" and a line at the end like ".zshenv ends".  Once you figure out which script is responsible, scatter some print statements to pin down the exact command.