He sought God during the days of Zechariah, who instructed him in the fear of God. As long as he sought the LORD, God gave him success. (2 Chronicles 26:5 NIVUK)
How nice if the formula was that simple: You + seeking God = success in everything
Who wouldn't be a Christian?
But let's hold on a minute and consider a few things. Firstly God knows the hearts of men & women. He knows they are deceitful above all things and He knows only too well our proclivity for self deceit and self interest ( yes, even us).....
Jeremiah 17:9 NIV
 The heart is deceitful above all things and beyond cure. Who can understand it?
God knows if we are seeking Him because it is really our hearts desire to be in His presence come what may....and this we see at the end of Habakkuk:
Habakkuk 3:17-18 NIV
 Though the fig tree does not bud and there are no grapes on the vines, though the olive crop fails and the fields produce no food, though there are no sheep in the pen and no cattle in the stalls,  yet I will rejoice in the Lord, I will be joyful in God my Saviour.
Here is a man who is intent upon seeking God whatever the future may hold . There is no pretending to have his heart set on God but really it's a front for seeking success.....
So, what is being said and what is meant in this 2 Chron 26?
Well I believe it's not complicated but nor is it superficially formulaic.
If the desire of our heart is God, and our first and only priority is to seek and do His will, to find and follow His agenda, then, to the extent of our integrity in this,we will be successful in what He calls us to do. Simples?