Those are glass catfish. They prefer to be in schools (6 or more) and are peaceful as far as I know, but I have never had them so I can't say for sure. I think they should be fine for your tank. Zebra danios are a nice fish and will occupy a different area of the tank so you could keep them and be ok - they also are quite active and that will give your other tank inhabitants more confidence. However, zebra danios are very hardy so if they are unhealthy, it might pay to check into why that is the case before you add any more fish. They might just be a bad batch but even so it would be risky to potentially sicken your new fish with a disease or make them ill with water conditions that are also making the danios unwell.
Oh, btw, it would be better to do your water tests before the water change so you can truly see what water parameters the fish are living in before you dilute it with fresh water.
Good luck.