The SCID ('Skid Cancelled Item Drop').
@Snasen recently told me about this neat way to z-drop bombs without the Zair coming out, I labbed it just then and I think it has amazing potential.
Essentially you just want to pull a bomb, run towards the edge of the stage/platform, return the joystick to neutral so that you enter a skid animation, then hit the grab button as early as frame 7 of the skid (frame 6 will give you a dash throw) and then hit forwards again as late as frame 15 (if you are too late Link will do a standing throw on frame 15). Link will then slide off the edge and z-drop the bomb without using Zair.
Very important to note! There are two kinds of skid animations depending on how long you run for before you return the joystick to neutral to start the skid. If you return the joystick to neutral between frames 14 to 25 (12 frames), 46 to 58 (13 frames), or 80 to 92 (13 frames) of the run animation, you will drop the bomb on the edge of the stage/platform because this skid animation has Link hold the bomb behind him.. Otherwise, if you return the joystick to neutral between frames 26 to 45 (20 frames), 59 to 79 (21 frames), or 93 to 112 (20 frames), you will drop the bomb off the edge of the stage/platform because Link holds the bomb out in front during this skid. With experience you will know roughly how far away you need to be, and in practice you will only be using the 14 to 25 and 26 to 45 frames windows. On the BF platforms it's difficult to find enough space to get into the 26 to 45 frame window, so you'll need to run the full length of the platform and delay the skid as long as possible (at which point you would be returning the joystick between frames 26 and 27; try to return the joystick to neutral on frame 28 and you'll do a flip off the edge on frame 27). Use this rough measurement to give you an idea of what spacing is required elsewhere.
Unfortunately the SCID is made more difficult on the Smashville platform when it is moving in the opposite direction of your run/skid. The faster it is moving, the less time you have to hit forwards to slip off, and at its fastest this means you have to hit forwards by frame 9 at the latest. If you are too late, Link won't slip off for the remainder of the skid and will then do a standing throw on frame 15.
Note also that you can feel free to hold the grab button, i.e. no need to let go of it immediately, and you should also hold forwards on the joystick just in case you still need to skid/slide over to the absolute edge of the stage/platform, at which point it will automatically z-drop the bomb and slide you off.
So you wanna seamlessly run off stage and Nair/Fair then Up-B out into the edge of the blast zone only to be saved from dying by the bomb blast? you can, just try to get the late skid once you've run far enough to make it easier to re-grab the bomb with the aerial, and be quick about inputting that aerial. How about laglessly dropping bombs as you maneuver around on the tri-platforms? go for it, and then depending on whether you want the bomb resting on the platform or raining down, you'll want to adjust your skid timing accordingly.
Stryker made a video to help you understand
https://youtu.be/bo69AjRYatc