Lemon zest is the very thin yellow layer on the rind of a lemon. It contains lemon oils which are very pungent. The white part of the rind under the zest is bitter and shouldn't be used for baking or...
Not effectively, the extract has a more intense flavor than fresh lemons.
use a teaspoon of lemon juice. The whole purpose of "rind" is to give extra flavor. Decrease the liquid by one teaspoon of the other wet ingredients.
yes
Try any citrus fruit, such as Lime or Orange.