Now a general plan 1.Se2 is too lazy, black Ra3 guards a field g3. In preventive maneuver third line will be  interfered twice. 

1.Kg7! (>2.Bxg6#) 

1. ... Bxb2+ (1…Be8, Bxc2 2.Bxe8, Rxc2) 

2.c3! Bxc3+ (2…Bc2 3.d3 etc. – see solution)  

3.Kh7! Bc2 4.d3! Bxd3.

At moment a general plan is sound: 

5.Se2! (>6.Sxg3#). Black has only 

5. … Be1, and 6.Bh6! (> 7.Sf4#) Bxe2 7.Bxg6# - model mate by all rest pieces by White.

No white checks!