WIP: avoid zip and unzip to improve the speed of get_indexer
- [x] closes #23735 #34531 
- [ ] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] improve the speed for get_index by avoiding some redundant zipping and unzipping