PSXE 2020 for macOS*: compilervars.sh currently does not support zsh. We're making the 'vars' scripts to be POSIX compliant in the future which will address this issue.
Simplest workaround is:
% bash -c 'source /opt/intel/bin/compilervars.sh intel64 ; exec zsh'
Which will end up with a new zsh instance, so if you exit from the new instance you will lose the env vars.
For more complete information about compiler optimizations, see our Optimization Notice.