flutter doctor - CocoaPods installed but not working

Question

using zsh - use to work in bash
brew doctor - Your system is ready to brew.
flutter doctor gives this error

[!] Xcode - develop for iOS and macOS (Xcode 12.2)
    ✗ CocoaPods installed but not working.
        You appear to have CocoaPods installed but it is not working.
        This can happen if the version of Ruby that CocoaPods was installed with is different from the one being used to invoke it.
        This can usually be fixed by re-installing CocoaPods. For more info, see https://github.com/flutter/flutter/issues/14293.
      To re-install CocoaPods, run:
        sudo gem install cocoapods  

sudo gem install cocoapods

Gives this error  
dyld: Library not loaded: /usr/local/opt/gmp4/lib/libgmp.3.5.2.dylib  
  Referenced from: /Users/puser/.rvm/rubies/ruby-2.5.1/bin/ruby  
  Reason: image not found  
zsh: abort      sudo gem install cocoapods  

I can't get this error above corrected - any suggestions?

which pod

/Users/puser/.rvm/rubies/ruby-2.5.1/bin/pod

which gem

gem () {
    \typeset result
    (
        \typeset rvmrc
        rvm_rvmrc_files=("/etc/rvmrc" "$HOME/.rvmrc") 
        if [[ -n "${rvm_prefix:-}" ]] && ! [[ "$HOME/.rvmrc" -ef "${rvm_prefix}/.rvmrc" ]]
        then
            rvm_rvmrc_files+=("${rvm_prefix}/.rvmrc") 
        fi
        for rvmrc in "${rvm_rvmrc_files[@]}"
        do
            [[ -s "${rvmrc}" ]] && source "${rvmrc}" || true
        done
        unset rvm_rvmrc_files
        command gem "$@"
    ) || result=$? 
    hash -r
    return ${result:-0}
}

which ruby

/Users/puser/.rvm/rubies/ruby-2.5.1/bin/ruby

Answer 1

Using the suggestion for this post, I was able to get cocoapods reinstalled with the commands below
gem native extension error while installing cocoapods

Open Terminal

curl -L https://get.rvm.io | bash -s stable

Reopen Terminal

rvm install ruby-2.6

rvm use ruby-2.6.5

rvm --default use 2.6.5

Then this installed cocoapods as expected

sudo gem install cocoapods