Azure Landing zone for service provider

Hello,
there's no direct way to answer your question however, from a landing zone perspective the same principals that apply to most of the organizations can be applied also for service providers, with some expections that might be directly related to the nature of the services and the way those services are offered.
I always consider building a landing zone is not a simple copy paste thing, it is a journey that require through understanding of the business and usage scenario. however, If you are willing to start I would advise you to start by checking and understanding the azure landing zone enterprise scale reference architecture as @pradeepDevia mentioned and try to customize it based on your needs.
https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/ready/enterprise-scale/

Regards
Charbel HANNA

this is a very open ended question to be answered , in general you can check the below link which has CAF and adoption in a basic manner https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/resources/tools-templates the above will give you a strategy , plan , checklist etc before you plan for adoption .