Well, the Exp. Share gives half of the experience gained by the lead Pokemon. So if the lead Pokemon gains 100% of its normal experience, that is boosted to 200% EXP. The other Pokemon holding a Lucky Egg would normally gain 50% of the EXP, but due to Lucky Egg, that's boosted to 100% EXP. So the Pokemon in the party holding the Lucky Egg gets the amount of EXP the lead Pokemon would have, were it not holding a Lucky Egg.
I hope that makes sense!