@foosel is correct. I think I assumed a little too much from your use of multiple routers and subnets and apparent understanding...I'm sorry about that. Your routers may be able to proxy or bridge your multicast traffic, but it's going to be something more advanced and it's not really something that you should be going into blindly.
Other things you could do would be to connect either the computer or the RPi to the other subnet instead of the one it is on (probably the RPi in this case) or turn router2 into a bridge if there isn't a particular reason why you have a second subnet.
If router1 doesn't have a mechanism for announcing custom DNS inside your network (some of them do, others only proxy DNS or pass on the DNS servers they receive from your ISP), your other option would be to use another server/RPi connected to Router1 as a DNS server for your entire network, and have both router1 and router2 specify it via DHCP and set it manually on any machines that don't use DHCP. Again, a bit more complicated than just doing it on your router, but still probably easier to figure out than multicast/zeroconf stuff, and I could probably dig up a guide for you somewhere on how to do it on a RPi if you have to go that route and don't know how. If one doesn't exist for the RPi and that's what you decide to use, I can figure out the steps and post the details for you (I've done it countless times, just not on a RPi).