Usually one uses Dawn, only the Blue liquid, for fleas. The Blue Dawn was/is used to get oil off the birds etc in the Gulf Oil Spill and other such disasters. Have to make sure it is only the Blue variety. You can do a YT search on using Blue Dawn for fleas. The fleas arpe supposed to drop right off. Maybe Zoe is very sensitive and another approach is necessary.
p.s. I have a Zack, Zeke, Zipp and Zoey, ranging from 3 to 15 yrs old

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Sorry about the duplicate info, slow on the draw (grin).
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Zack, Zeke, Zoey, Zipp RIP 6/28/12