Combine flour, yeast, salt, butter, sugar, mastic, mahlab, cinnamon, and orange zest in a bowl.
Gradually mix in 150ml of water and 150ml of milk to form a soft dough.
Fold in the sultanas and knead on a floured surface until pliable.
Shape into a ball and rest for at least one hour until doubled in size.
Divide dough into three strands and plait them together on a lined baking tray.
Let the plait rise for another hour until doubled in size.
Preheat the oven to 210°C.
Apply egg wash and press the red hardboiled eggs into the dough plait.
Bake for 20 to 25 minutes then cool on a wire rack.