How do I format a big disk (4TB) for use in both macOS and a Raspberry Pi?
For the partition table, you'll want to use the "GUID Partition Table" (called GUID Partition Map in macOS Disk Utility, and GPT on Linux/Raspberry Pi). The MBR partition table you've have been suggested indeed does not work for partitions larger than 2 TB.

For the file system itself, you'll want to use ExFAT. It is a relatively simple file system understood by both macOS and Linux/Raspberry Pi without many of the size limitations of earlier MS-DOS style filesystems such as FAT16 and FAT32.