I recently played a gig where my stand partner had Zyex strings- I was very impressed with their sound and I thought they bowed well.
That said, I recently switched from Flex 92 to Spiros on my orchestra bass- I have two observations which may be helpful:
1- How old are the Zyex strings? They may need to mellow out, wear in, what ever...My arco technique is pretty solid but it still took some time and effort for me to acclimate to the difference, and for the Spiros to mellow. Maybe you just need to wait a while longer?
2- How old is your bow hair? I just had a rehair done and I found it immediately much easier to get a good sound and quick start. I did switch from black hair to cinnamon though...not sure if that has much to do with it...and maybe that's something for another thread?