Been using Zellij for awhile and it is delightful! I am only a moderate terminal user, but I really like having some basic multiplexing features if I need them. My brain just could not hold onto the necessary tmux key combos with only intermittent use. Instead I find the Zellij commands to be more intuitive (and more discoverable thanks to the handy prompts...)
Open man page for tmux. Search for split window.
Launch tmux and split window. Open man page for tmux in 2nd window.