Congrats! Having 2 little ones has worked out beautifully for us!
ZP is a great choice for us as well!
Both girls came to us on kibble. Neither were good quality although BOTH breeders felt strongly that theirs was the best. Once I checked (as you have done) and informed myself versus falling for marketing and advertising, I discovered what you have.
Mine both began eating it at about 14 weeks, but I certainly could have started earlier. It is an all life stages food.
The squares are like 1/2 inch (sorry, I do not know the metric equivalent!) VERY thin squares that are like beef jerky.
I add warm water to the bowls. They have also eaten it dry and do so with NO issue. At night they get a scoop of Nupro added.
You will feed them by weight. A scoop comes in each bag (I now have a collection!) My girls are 7 and close to 8 months and weigh a bit over 3 pounds (one is 3.2lbs., 1.45 kgs. and the other 3.4 lbs., 1.55 kgs.) and they get a bit less than 1/2 scoop (just under the line on the scoop) twice a day.
Because one of my girls had chronic colitis (learned that she cannot eat kibble nor canned food), I have not yet introduced add-ins to the food but I would say that many, if not most do. I am just afraid to make any change for now since this food COMPLETELY tuned her health around.
Those who add, include cottage cheese, ground meats, scrambled eggs and more. If you search ZP or Ziwipeak, you will find add-ins that people feed.
We have the lamb and the venison treats. The lamb is kind of rich so I limit how much I give my sensitive tummy one (Hope). We also give Stella & Chewy's Carnivore Kisses Chicke (single ingredient dehydrated) and Carnivore Crunch Chicken which contains organs and bone meal.
Hope this helps you some!