With classic diffie-hellman it's possible do it with more than two parties. Is this applicable to elliptic curve diffie hellman?
I'm guessing not.
With ECDH you have a scalar number as the private key and an x, y coordinate (or just x coordinate in the case of Curve25519) as the public key. You multiply the coordinate by the scalar and you get a new coordinate. The x coordinate of that is the shared secret.
If you had two public keys and one private / public ECDH key pair... if you didn't discard the y coordinate you could multiply one of the public key coordinates by the private key but then it's not clear what you would do with the other public key coordinate. Maybe there's nothing you can really do to facilitate ECDH for more than two parties?