lets make some corrections here...

** ** ***Today Zygote is known as Daz3d. **

no. Daz started as a subdivsion of Zygote which was then bought out and became Daz3d. Zygote is still in operation as it's own company seperate from Daz suppling high end medical imaging models.

Without a business relation to poser daz3d found i necessary to have some sort of render engine for people to use their products with.  Hence DAZ|Studio was created.
no. Posers future was in the balance around the launch time of Poser 5, (with Egisys forcing CL to release a buggy poser 5 and then going bust, which forced the sale of Curious Labs to E-Frontier. Curious Labs no longer exists having been absorbed into EF and the name Curious Labs now dropped). with the time gap between Poser Pro Pack and Poser Five, Daz decided to start development of their own poser program incase Poser went off the market and protect their own interests. that program is Daz Studio.