Apparently Kamen Rider Zi-O: Over Quarter possibly will not be consider CANNON, it will be consider a stand-alone/alternate time line.

Kamen Rider Zi-O: Taking place between episodes 44 & 45 would be disregarding its strengths as a movie, but making it a completely standalone story unrelated to the tv series would be disregarding the strength of Zi-O as a tv series. So, this movie follows a third path, which hasn't been officially confirmed yet.