Connecting 2024 Mac mini a Apple Studio Display and an old 2020 iMac 5k with Thuderbolt

I want to be able to use both my 27in Apple Studio Display and my 2020 iMac 27in 5K with my new 2024 Mac Mini.

I want to have both displays at 2560 x 1440 resolution most of the time.

I currently have the main display as the Studio Display connected via the single Thunderbolt outlet with a thunderbolt cable and the extended display as the iMac connected to the USB port on the back of the Studio Display to the Thunderbolt port on the back of the iMac.

It does not appear to matter what order I connect the iMac, I can't get it to offer higher than 1920 x 1080 resolution.

There is only one thunderbolt port on the back of the Mac Mini but two thunder bolt ports on the back of the iMac, and one thunderbolt port on the back of the Studio Display. The cables are new thunderbolt cables.

How can I get maxium resolution through both my displays?