MagicSave does not work. Following these instructions to use SED does not work either.
According to this Github post, the Invizimals: Shadow Zone save data must be opened on a PSP with the original MAC address. So, I think to open the save file, we must spoof/change the MAC address of the PSP console to match the MAC address in the downloaded save data. But even after decrypting the downloaded save data with SED, I cannot locate the MAC address when opening it in a hex editor.