i think you are right about some of this. i didn't read much of the crossovers because i follow specific characters (barry allen, arthur curry, carter hall, and billy batson) i don't typically like the alternate versions. we are led to believe that eobard thawne has such mastery of time that he can manipulate events down to the second--probably faster. yes, i think some of the details were lost in the 'quickness' of the series' runs.
Since Zoom didn't do squat here, and all the changes were caused by Barry trying to save his Mom, it doesn't matter how Zoom did it. I'll assume that the Speed Force disruption caused the Earth's rotation to slow, or the rocket to slow, or both, causing it to land elsewhere.
Of course, it's almost certainly all Pandora's fault...