Don't forget that zones do not contain all of the digits. Familiarity with basic soduku solving techniques is good, but advanced strategies are not needed and often not possible without 3x3 blocks.
Look for zones that are almost complete to see if they require a specific digit to make evens or odds win.
The largest and smallest digits are most likely to cause problems. Check if an 8 or 9 would be too much for a zone, or if something more than 1 or 2 is needed.
Remember that successful gerrymandering means most of the odd zones have way too many odd numbers, so they are less likely to produce useful contradictions.
Once you can eliminate any possibility, check if that forces something else.