My camera case is arranged so that I keep the 300mm on the camera body inside it: consequently when I enter a zoo and sit down on the nearest seat, that combination comes out first. What happens next depends which zoo I'm at and which route I choose. When everything opens up after lockdown, if I'm at Paignton or London I will go straight for the reptiles, which happen to be close to the entrances of those zoos, so I will change to the 105mm macro lens, as it is the one I use most often for indoor work. As I have written here before, I prefer to see the reptiles at the start and end of a zoo visit because most of them move relatively little, so an animal which is hiding or not showing well in the morning may be posing nicely later in the afternoon (or vice versa). On the other hand when I am just walking around a zoo, the 55-200 zoom is often the best choice: but I find that I change lenses quite frequently and I generally use all of them at some time in a visit - except for the teleconverter, which I only use occasionally with the 300mm, but it can be very useful and it's so small that it is no bother to carry.
I find the monopod more and more useful. I rarely use the 300mm without it, but it is excellent for use with shorter lenses in low light situations, or when I want to choose a slow shutter speed to get good depth of field. My worst moment in a zoo for a long time was when I sat down after arriving at Pairi Daiza for the first time in October 2019. I had checked my kit on the train, but I found that the adjusting nut on the monopod's tilt head was missing

I walked back to the entrance, but could not find it, so I realised it I had fallen off on the walk from the station. I just had to strap the useless monopod back on the camera bag, take a deep breath and do the best I could. I had two pretty good days at PD and a nice day at Antwerp too, but I know I could have got better photos of the Spix's macaws if had used the monopod. I did find the nut on the way back to the station, but not the washer which fitted between the head and the nut. Next time I will keep the head in my bag and screw it place inside the zoo.