I have installed Zorin OS 16 and AV Linux with the following partition layout: 512 MB EFI mounted at /boot/efi, then two ext4 partitions, 250 GB each. The root of Zorin OS was installed on the first one and I just now installed the root of AV Linux on the second one. I prefer the grub menu that comes with Zorin, so I opted out of setting up the AV Linux bootloader. My two problems here have to do with configuring the grub without ruining it: How do I have the grub menu load on each power on instead of skipping it, and how do I add AV Linux to the list?
The computer is 64-bit, and AV Linux is built from MX Linux 21. They're installed on hd0 (sda) and there are 3 partitions: grub menu is sda1, Zorin is sda2, and AV Linux is sda3. If I'm missing any relevant info, please ask me for it so I can try my best to provide it to you. I'm relatively new to linux but I'm usually quick with understanding so please be patient with me.