In case anyone is working on getting a split tunnel working from a Meraki Z3 (or Z1) this is working for me.

[this would likely work with a MX device, but I don't have one of those so I can't confirm],

Meraki side of things / Site-to-Site VPN

-Type: HUB (Mesh)

-NAT Transversal: Automatic

-OSPF: Disabled

-Inbound Firewall logging: Enabled

-IKEv1

-Public IP (ER605 external IP)

-Private Subnets (other side subnet)

-Preshared secret (whatever you want here)

-Availability: All Networks

-IPsec Policies: Custom (see below)

ER605 side of things, VPN, IPsec.

Policy Name: whatever you want

Remote Gateway: (Meraki side external IP/domain name)

Hope this is helpful for somebody.

I've connected to my dad's home network this way, makes it easy to troubleshoot as well as share media.

I get between 1.7MBps to 2.0MBps over this link when transfering home videos, tested with larger 1GB/2GB files.