I know that the specifications of the Microsoft PE/DLL/DOS-MZ files states that the two first bytes of a PE/DLL/DOS-MZ file is `MZ` (0x4d,0x5a`) or`ZM`(`0x5a,0x4d`).

The problem with such a small signature is that a lot of other files may match the same specification and a test based only on this two first bytes quickly tends to be inconclusive.

So, my question is simple, after testing that the two first bytes are `MZ` (or `ZM`), what other, more reliable, test can be performed to check that the file is a PE/DLL/DOS-MZ?