Wow, never autopush all your tags. What a terrible idea! Once a tag escapes into the wild, it's so hard to ever get rid of it. Pushing a tag should require two people turning keys simultaneously or something, honestly.

zdiff3 is also NOT some kind of generic improvement over diff3, like swapping diff algorithms is sorta a generic improvement. It behaves very differently; if you have

    [original]
    this is a line

    [left branch]
    This is a line.
    This is a second line.

    [right branch]
    This is a line.
    This is another line.

then diff3 shows

    <<<<<<<
    This is a line.
    This is a second line.
    |||||||
    this is a line
    =======
    This is a line.
    This is another line.
    >>>>>>>

while zdiff3 modifies this in a very matter-of-personal-taste way to:

    This is a line.
    <<<<<<<
    This is a second line.
    |||||||
    this is a line
    =======
    This is another line.
    >>>>>>>

This is incredibly bizarre to my eye, but some prefer how it's already "partially resolved" for them. But it's hardly something to swap in thoughtlessly for the other!