Welcome to the Zoom Community, @lgvtheory.
You don’t mention what type of Zoom license you have, but none of the regular user licenses will allow someone to run 4 simultaneous meetings. Pro and Basic accounts are limited to 1, and most others are limited to 2.
How many people are involved in these 4 meetings? Is registration paid, free, or if the event sponsored In any way? If so, running a Zoom Event could accommodate 4 simultaneous sessions. If you can afford to pay around $2.50 per person (less in larger quantities), this might be an option for you.
Note: Setup for a Zoom Events is non-trivial the first few times; after some experience or with the right guidance, it’s not really difficult. I have a client setting up a 10-day event in March expecting around 1,000 attendees, doing 95% of the setup on his own and with non-technical volunteers.