so i was curious about higher dimensions and watched a few videos about it on youtube when i realized that Z being a 6th dimensional being explains a lot of the weirdness of his plot line.
like the picture above and how he got Misaki from the future.
humans are 4 dimensional beings although some people often mistake them for 3rd.
length ,height, width, those are the 3 spatial dimensions the 4th is time.
humans experience the spacial dimensions and also the flow of time making them 3rd dimensional beings able to perceive the 4th but they can't move through it freely.
to move through a dimension freely you have to be a dimension higher.
in this case Z is in the 5th dimension. he is in a depiction of the fifth dimension outside the flow of time of the 3rd dimension. from here he can observe time going forward and backwards without making alterations and he can go into it at any point. if he was a dimension higher he could time travel through all of the possible time lines that could be spawned from the original creation of this timeline and travel between them but he can' so he is only in the 5th observing the 4th and unable to move through the 6th to travel through the 5th