How does the zygote divide much faster than other cells?
A zygote generally has a lot of nutrients, essential biomolecules like RNA and proteins and cytoplasmic organelles for rapid division. So the cell does not grow and divide but rather undergoes "cleavage" (there is no G1 phase of cell cycle). However, it still undergoes DNA replication. And yes, DNA replication is fast because it is initiated at once from several parts (origins of replication) of the long DNA (it still takes a few hours&dagger; ).


 &dagger; See:


Confusion about the duration of different phases of the cell cycle such as G1, G2 &amp; S
Time spent in phases of cell cycle