pyenv init
と入力すると、下のように表示されます。
$ pyenv init [ruby-2.6.3p62]
# (The below instructions are intended for common
# shell setups. See the README for more guidance
# if they don't apply and/or don't work for you.)
# Add pyenv executable to PATH and
# enable shims by adding the following
# to ~/.profile and ~/.zprofile:
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init --path)"
# Load pyenv into the shell by adding
# the following to ~/.zshrc:
eval "$(pyenv init -)"
# Make sure to restart your entire logon session
# for changes to profile files to take effect.
ここに記載されているように、~/.profile、~/.zprofileの最後に
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init --path)"
を追加してターミナルを再起動したらどうでしょうか。