ZeroTier clients don’t use DHCP to get addresses, they use the assignment from my.zerotier.com. You can always start some DHCP client (dh-client, etc) on the interface on something like Linux, but that’s is not possible with mobile (and more difficult on Windows/Mac). Client IP address are assigned by ZeroTier Central next to the device in “Members”.
You can manually assign clients an IP address in ZeroTier from your LAN range in one way. But you can also use auto-assignment on my.zerotier.com with the bridged LAN’s prefix. To do this, “split” the /ip/pool so that it doesn’t overlap with the auto-assignment in my.zerotier.com. e.g. on /ip/pool use 192.168.88.101-192.168.88.199 while in ZeroTier Central use 192.168.88.200-249 (or whatever split you want).
It’s important that you do NOT assign an IP address to the ZeroTier interface on the Mikrotik if it’s bridged. Its IP address comes from either the VLAN or bridge interface’s IP address.
For more detailed answer, see http://forum.mikrotik.com/t/zerotier-on-mikrotik-a-rosetta-stone-v7-1-1/155978/1 under “Use Case C”