Can I Continue Zerolac Or Switch To Nan Pro Or Lactogen 2 For My Baby?

Hi, i need suggestion for which formula milk shud i give to my 7 month old baby? At 3 months of age we gave Lactogen 1 and it suits her. Then at the age of 6 months we gave A2 cow milk and Amul Shakti but she started having diarrhea. So we changed to Nan pro. With Nan pro 3 days were fine but then 4th day she started doing 5 to 6 times green blackish potty so doctor suggested zerolac... now ots 2nd day with zerolac she is doing fine. My question is shud i continue to give zerolac as daily milk? Or can i switch to Nan pro or lactogen 2 ??