Broadband speed decreases after connecting two routers

Is your Zyxel router configured to be used as a bridge?

Is your Netgear router capable of using wi-fi? If so, disable it or configure it so that the channel is not the same as your Zyxel's.

yes, zyxel router is set in bridge mode and channel selection in both routers is set on "auto".

Do you have normal speed while connected directly to the Netgear router?

If you don't use your Netgear's wi-fi, you should disable it, because you have an access point already. Is there something in your Zyxel's manual saying how to turn it into an access point? Did you do all needed configuration?

i need to use both router's wifi as both r on different floors in building. yes.when using netgear only i get the normal speed.......but signal doesnt reach to the another floor. so i need the another router which is properly set to access point as per the mannual. but it makes the network slow.

tell me one thing.........should i insert the ethernet cable in wlan port or in one of the lan port in zyxel router. i hv inserted in wlan port bcz when i insert in lan port it doesnt seen to work. internet or wlan light doesnt lit.