下面是一个使用troposphere创建多可用区的AWS RDS示例代码：

from troposphere import Template, Parameter, Ref, Tags, AWS_REGION, AWSStackName
from troposphere.rds import DBInstance, DBSubnetGroup, VPCSecurityGroup, DBInstanceIdentifier

template = Template()

subnet_group = template.add_resource(DBSubnetGroup(
    "SubnetGroup",
    DBSubnetGroupDescription="Subnet group for RDS",
    SubnetIds=["subnet-xxxxxxxx", "subnet-yyyyyyyy"]  # Replace with your subnet IDs
))

security_group = template.add_resource(VPCSecurityGroup(
    "SecurityGroup",
    GroupDescription="Security group for RDS",
    VpcId="vpc-xxxxxxxx"  # Replace with your VPC ID
))

db_instance = template.add_resource(DBInstance(
    "DBInstance",
    DBName="mydatabase",
    DBInstanceIdentifier=Ref(AWSStackName),
    AllocatedStorage=20,
    DBInstanceClass="db.t2.micro",
    Engine="MySQL",
    EngineVersion="5.7",
    MasterUsername="admin",
    MasterUserPassword="password",
    VPCSecurityGroups=[Ref(security_group)],
    DBSubnetGroupName=Ref(subnet_group),
    Tags=Tags(
        Name="MyRDSInstance",
        Environment="Production"
    )
))

print(template.to_json())

这段代码创建了一个RDS实例，该实例在两个指定的子网中运行，并使用指定的安全组。您需要将代码中的替换为您自己的子网ID和VPC ID。此外，您还可以根据需要调整其他RDS实例的属性，例如数据库名称，存储量，实例类型等。

请注意，这只是一个示例代码，您需要使用AWS CloudFormation等工具来部署和执行此代码。