Practical flow: trigger on finalized transcript (Google Drive or Sheets), Loop by Zapier over chapters, call ElevenLabs via Webhooks with chunked text, then save MP3 to Drive. Rate-limit handling: use Loop + “Delay For” (e.g., 1–3s between requests), stop/retry on 429 with exponential backoff (2s, 4s, 8s) and a max retry count. Filename convention: COURSEID_chapter001_ShortTitle_v1_YYYYMMDD.mp3 (zero-pad chapters, underscore spaces, include version/date).