Ingress traffic is tagged on a trunk port (Ether1) with VLANs 1, 2, 3, and 4.
Egress traffic is on another trunk port (Ether5) with: vlan 5 and 6
Outer VLAN tag 5 - for VLAN 1 and VLAN 3 (as inner tags).
Outer VLAN tag 6 - for VLAN 2 and VLAN 4 (as inner tags).
This requires Q-in-Q (802.1ad) VLAN configuration, where outer VLAN tags (S-TAGs) encapsulate inner VLAN tags (C-TAGs).
How this is achievable on single microtik unit