Just ask it to figure it out step-by-step and to remove accents:

GPT-4:

Figure this out step by step and check your work: Remove the accents and tell me if this a palindrome: Élu par cette crapule

GPT-3.5 (Needs to know that removing spaces and lowercasing is okay):

Figure this out step by step and check your work: Lowercase it and remove the accents and spaces and tell me if this a palindrome: Élu par cette crapule