Sooo....
Math time!
Ahri;
Q: 140+0.35AP
Q: 140+0.35AP as true damage
W: 224+0.48AP
E: 180+0.4AP
E: +20% damage
R: 360+1.5AP
Total: 1044+3.08AP
Adjusted total: 1252+3.696
Zoeh:
Passive: 135+0.32AP
Q: Min: 150+0.6AP
Q: Max: 375+1.5AP
W:195+0.55AP
E: Min: 220+0.4AP
E: Max: 440+0.8AP
Total min: 700+1.87AP
Total max: 1145+3.17AP
Comparison:
A minimum zoe combo deals ~65% of an ahri who uses her E last.
A maximum zoe combo deals ~90% of an ahri who used her E first.
(This comparison only compares in-kit damage numbers, not mobility and CC, of which Ahri has more mobility by far and zoe has more CC. They are both roughly the same level of safe as well, with Ahri being slightly safer)