So, while all of this timeline-altering trouble is going on, Nate Grey is sitting in his pocket dimension outside the timestream that is being manipulated by Sinister, and is thereby unaffected by it.

Source: https://screenrant.com/cyclops-son-theory-return-sins-sinister-x-men/

Zolomon begged West to use a time traveling cosmic treadmill (yes, really) to go back into the past and prevent his injury, but Wally refused, as he didn’t want to mess up the timestream.

Source: https://www.themarysue.com/who-is-zoom-in-the-flash-answered/