Do I have to make a reservation?

Yes and no. By reservation, it means you buy your tickets and print them prior to arriving at the zoo. It still looks like you can buy a ticket at the gate once you pass through the medical screening but I would highly advise against it as there is a limited number of tickets each day to keep the park at the current allowed capacity.

Yes

You absolutely 💯need a reservation. We had to show our tickets at medical screening.

I would advise making a reservation to make sure you get in. You can buy tickets online.