Bug?
It looks to me that the name of the zip file used in the first and the last command were intended to be the same, that is the ${drt}/db-$(date +\%F-\%T).zip part:
mysqldump ... | zip ${drt}/db-$(date +\%F-\%T).zip ... rm -rf ${drt}/db-$(date +\%F-\%T).zip
They will only be the same if the mysqldump and rm commands run within the same second.
Don't repeat yourself
If a non-trivial command is expected to return the same value every time you run it, then extract it to a variable. Not only to save unnecessary processing power, but also to keep the non-trivial logic in one place, so that it's easy to change if ever needed, in one place.
Double-quote command arguments
It's a good rule of thumb to double-quote command arguments when they contain variables, to protect yourself from unintended word splitting and glob expansions.
Useless flags
In rm -rf ${drt}/db-$(date +\%F-\%T).zip,
since we're deleting a file, not a directory,
the -r flag is useless.
Avoid useless flags.
Understand the meaning of every flag you use,
and only use a flag if it's really needed.
Alternative solution
I suggest to write like this:
#!/bin/bash
date=$(date +\%F-\%T)
mysqldump -u root -p --all-databases | zip "${drt}/db-$date.zip"
zip -r "all_zipped-$date.zip" "${drt}"/ -x "*/cache/*"
rm -f "${drt}/db-$date.zip"
