Use is approved for quartz tile, but the product is intended for grout and manufacturer instructions specify limited dwell time and no rinsing.
Why
Zep explicitly states the product is safe for quartz tile. No contradictory chemistry or surface warning is provided.
What to do
Use only as directed: apply to grout or the targeted area for 2–5 minutes, then brush or wipe/dry mop; do not rinse. Avoid assuming approval for unsealed or non-tile quartz surfaces; spot-test if the finish is uncertain.
pH
Not disclosed in retrieved manufacturer evidence.
Relevant chemistry
No named chemistry or pH was shown in the retrieved manufacturer evidence.
Source: official product page ↗