Hi, welcome to Zscaler Community.
Firstly i would recommend you to raise a ticket with our TAC regarding this issue along with the supporting snapshot like ip.zscaler.com.
Zscaler would not block any website unless the URL filtering policy of your organization says so.
Zscaler IP might get blocked at destination end due to various reasons. Sometimes we have seen IDRBT regulatory issues blocking a specific IP address of Zscaler. Not sure why but banks follow this regulatory.
How Zscaler can help is, with the support ticket our TAC team would reach out to the destination webmaster requesting to lift the block of our IPs in their FW or IPS. Please also let us know what bank site you are unable to access.