All information relates to the specific ROM: “Metroid - Zero Mission (U) [!].gba”, it has CRC
5DE8536AFE1F0078EE6FE1089F890E8C7AA0A6E8 and internal name “ZEROMISSIONE”. ROM size is 8,388,608 bytes.
A list of guides created by the community, from manuals on the tools themselves to advanced guides relating to ASM, it's all here.
Manuals of the workings of all the editors and utilities available to you, detailing all their functions.
These guides cover all the basic things around editing Metroid Zero Mission, as well as serving as a good starting point for learning how to get into Metroid Zero Missionhacking!
These guides assume you have a good basic knowledge about editing Metroid Zero Mission already, you should probably be comfortable with using MAGE or Double Helix by now and be moving onto using tools like a hex editor.
These guides could be pretty complex, you should probably be comfortable with assembly by now.
This segment is reserved for technical information on Metroid Zero Mission, to be used as reference material for hackers, or for the curious wanting to know what makes Samus tick, or possibly you are interested in making a fan game and want to know how Metroid Zero Mission does things!