Looks nice! I paid roofers to put a new shingle roof on my house and they re-used old copper flashing around my brick chimney. Now in middle of winter, its leaking water all the way downstairs to my garage. I thought they would install all new flashing like you did. Guess I was wrong for expecting a professional job!
I.might add ( you maynhave added. But I didn't see it ) a self adhering seal under the right lower side where the little shingle end segments meet the chimney. Those are always s problem for us in high winds and storms.
Sorry Fresh mortar will never hold up. Mortar does not adhere to metal. To do it correctly you have to use asphalt roof cement and fill the cut first with it then install metal and then top caulk.
counter flashing should be stepped not one piece , if you you make it one piece it can move and crack brick and you should mortar not caulk it not bad job it will work I was just taught different
Learn how to give your lower flashing a nice bend to the point that there is gonna be enought pressure on it and you are not going to have to put any nails throught it. n you should only cut throught the mortar not the brick G