Heat oven to 350°F. Coat egg pans with cooking spray. Sift flour, baking powder, salt into bowl.
Beat shortening in large bowl until smooth. Beat in sugar until fluffy. Beat in whites, one at a time.
Mix milk, vanilla, zest and juice in bowl (may look curdled). On low speed, beat flour mixture in 3 additions alternating with milk mixture, into egg white mixture. Divide batter between pans.
Bake in 350°F oven 40 to 45 minutes, until cakes test clean with pick. Cool cakes in pans on rack 10 minutes. Unmold cakes. Let cool.
Beat shortening, butter, sugar, milk, extract and zest in bowl until smooth and spreadable.
Trim 1-1/2-inch piece off one end of each cake to form base. Sandwich halves together with 1/2 cup frosting, first trimming flat sides even, as needed. Stand sandwiched cake on flat base. Cut broken egg edge off top quarter of cake; cut off top. Scoop out small portion of cake in center of base of egg. Reserve 1 cup frosting; use remainder to frost outside of cake and cap. Place cap in the freezer for 10 minutes to firm.
Tint 2 tablespoons of reserved frosting green. Divide remaining reserved frosting in half. Tint half pink, the other blue. Spoon tinted frostings into 3 separate pastry bags fitted with decorative tips. Pipe patterns on cake.
Knead coconut and few drops green coloring in plastic bag. Place some grass inside scooped-out portion of base, reserving remainder. Remove 1 tablespoon marzipan; tint 1 teaspoon brown (chick eyes) and 2 teaspoons orange (beaks, crowns). Tint remainder yellow.
Roll two 1-tablespoon portions yellow marzipan between palms into balls. Attach to make chick. Form wings with more yellow marzipan. Make orange beak and crown, and brown eyes from marzipan; attach to head. Repeat to make 3 or 4 chicks total. Place in grass in top of cake base. Scatter remaining grass around bottom of cake on platter.
3D Egg Pan set available from Wilton; 800/794-5866 or wwww.wilton.com.