CAN I USE ZINSSER ALL COAT EXTERIOR SATIN ,WATER BASE, FOR THE INSIDE OF THE SHOWER CUBICLE .IT IS TO PAINT OVER BLACK SLATE TILES WITH THE ANTHRACITE GREY. ITS ONLY ONE ROW OF 10X10CM . SHOULD I PAINT THE WHITE GROUT AS WELL
Unfortunately no, this is not suitable.
But assuming the tiles are bare, clean, dry, sound and prepared as detailed in the technical data sheet you could consider the Rust-Oleum Tile Transformation Kit.