Actually, it is a hard question to answer just because either verb has multiple meanings. And they partially intersect.

Antonio, could you provide a context to make it easier to explain?

Otherwise,
входить can mean:
- to enter (a place) by walking: входить в комнату;
- to be a member of, to take part in: see Maximixiv's example.

заходить can mean:
- to make a short visit to a place by walking: заходить в магазин по дороге домой;
- the same as "входить" in its first meaning, this is sometimes used colloquially: можете заходить (в комнату)! = можете входить (в комнату)!
- to walk into a place behind something: заходить за дом;
- to walk too far: не заходи слишком далеко!
- to go too far (figuratively): Он зашёл слишком далеко со своими претензиями!