The first option is Keep all unread messages on top.
The second option is Move message with new replies to the bottom of the chat.
This option moves messages which have new replies to the bottom of the chat history.
To pull up the configs, punch your user icon in the top-right corner, then punch configs.
To access Zooms prefs, select your user icon, then on prefs in the dropdown menu.
Once in the controls, switch to the Chat tab.
Having both of these options disabled will ensure that all messages will be displayed in chronological order.
