I would suppose so, for the IPv6 and mask part.
I have no idea if you can use lists here.
Also, I do not think this rule is the place where you can set IPv4 forwarding, you would need a separate DNAT redirect for that.
A few days ago I had to work out how to forward IPv4 and IPv6 connections, and I wrote it down here at chapters 7.g) and 7.h). Maybe these examples are of some help.
Regarding your IPv6 and mask, chapter 1.1 of this RFC indicates that a positive mask number means "the first n bits", so I am inclined to assume a negative number means "the last n bits".
From that I also assume that the masked address bits (i.e. the ones where the corresponding mask bit is 1) are the ones that are tested, and the others are ignored.
As @jow already pointed out, you can alternatively supply the mask in the same hexadecimal notation as the address. See also this comment on this superuser.com answer.
If it still does not work, maybe you need to set src_dport=5060? Otherwise it looks to me as if you want to route?/forward? all incoming connections (any port) to your destination at port 5060.
I have never tried anything like this, and I do not know if it makes sense.