Wireless router on DMZ

Wireless router on DMZ not able to resolve DNS. Connected to the router locally I can ping public IP addresses but can not browse using the browser. Please advise!

C:\>nslookup 10.200.215.254
DNS request timed out.
    timeout was 2 seconds.
Server:  UnKnown
Address:  10.200.215.254

DNS request timed out.
    timeout was 2 seconds.
*** Request to UnKnown timed-out
--------------------------------------------------------
C:\>nslookup 75.75.75.75
DNS request timed out.
    timeout was 2 seconds.
Server:  UnKnown
Address:  10.200.215.254
DNS request timed out.
    timeout was 2 seconds.
*** Request to UnKnown timed-out
-----------------------------------------------------------------
C:\>ping 75.75.75.75

Pinging 75.75.75.75 with 32 bytes of data:
Reply from 75.75.75.75: bytes=32 time=22ms TTL=54
Reply from 75.75.75.75: bytes=32 time=21ms TTL=54
Reply from 75.75.75.75: bytes=32 time=21ms TTL=54
Reply from 75.75.75.75: bytes=32 time=20ms TTL=54

Ping statistics for 75.75.75.75:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 20ms, Maximum = 22ms, Average = 21ms

C:\>tracert 75.75.75.75

Tracing route to 75.75.75.75 over a maximum of 30 hops

  1     1 ms     1 ms     1 ms  10.200.215.1
  2     1 ms     1 ms     1 ms  10.200.215.254
  3     9 ms    10 ms     9 ms  10.200.40.1
  4     8 ms     8 ms     9 ms  192.168.7.53
  .
.

  9    23 ms    22 ms    22 ms  68.86.90.214
 10    23 ms    23 ms    21 ms  96.108.37.118
 11    22 ms    21 ms    21 ms  68.87.225.66
 12    20 ms    21 ms    21 ms  75.75.75.75

Trace complete.
------------------------------------------------------------
C:\>tracert www.yahoo.com
Unable to resolve target system name www.yahoo.com.
---------------------------------------------------------
C:\>ipconfig /all
Ethernet adapter Ethernet:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : R
   Physical Address. . . . . . . . . : 
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 192.168.6.22(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Friday, November 17, 2017 9:50:42 AM
   Lease Expires . . . . . . . . . . : Saturday, November 18, 2017 9:50:42 AM
   Default Gateway . . . . . . . . . : 192.168.6.1
   DHCP Server . . . . . . . . . . . : 192.168.6.1
   DNS Servers . . . . . . . . . . . : 10.200.215.254
                                       75.75.75.75
   NetBIOS over Tcpip. . . . . . . . : Enabled

 ---------------------------------------------------

---------------------------------

Fortinet DMZ interface:

IP/Net mask : 10.200.215.254/255.255.255.0

Policy: DMZ2Wan--- sources-all, dest-all,services-all  NAT enabled

No security profiles.

-----------------------------

Wireless router info: Internet: IP 10.200.215.1 subnet: 255.255.255.0 gtwy: 10.200.215.254 DNS1: 10.200.215.254 DNS2: 75.75.75.75 Lan: IP 192.168.6.1 mask: 255.255.255.0 DHCP - 192.168.6.20-192.168.6.30