If it is just a tiny zip tie, toenail cutters work good for cutting them ... some are spiral plastic that you can unwind, some are small rubber bands ...
Depending on the type of band it is ... you will need to monitor it so it doesn't get too tight and cut off circulation ... some people use colored plastic zip ties ... which need to be cut off when they get too tight from the chick growing, usually they install a new one, and leave it loose...