If the seals and the trumpets are simultaneous, with an angel sounding a trumpet whenever a seal is opened, then seal one coincides with trumpet 1, seal two coincides with trumpet 2, seal three coincides with trumpet 3 and so on.
When the first seal is broken, the Antichrist is revealed. The first trumpet sounds and then a third of the Earth’s trees and grass is burnt up. When the second seal is broken, war is unleashed. The second trumpet sounds and a third of the sea turns to blood and a third of the sea creatures die and a third of the ships are destroyed. When the third seal is opened, famine is rampant. The third trumpet sounds and a star falls from the sky turning a third of the fresh waters bitter. When the fourth seal is opened, death abounds. The fourth trumpet sounds and a third of the sky is darkened blocking the light of the sun and moon. When the fifth seal is opened the martyrs cry out. The fifth trumpet sounds and locusts come out of the abyss to torment those with the mark of the beast for 5 months. When the sixth seal is opened, signs appear in the sky and earthquakes shake the Earth. Men try to hide from Gods impending wrath. The sixth trumpet sounds – 200 million mounted troops are released to kill one third of all mankind. Still man does not repent!
Next, the 144000 Jews are sealed and a great multitude appear in heaven. When the seventh seal was opened, there was silence in heaven for half an hour. The seventh trumpet sounds as the seventh seal is opened and the mystery of God is accomplished. The little scroll is opened, the two witnesses finish prophesying for 1260 days and then they are raptured. Jerusalem has been trampled for 42 months. The time for judging the dead in Christ has come. The church is raptured and the first resurrection takes place. God pours out the seven bowls of his wrath as he leads an army of believers to strike down the nations. The nations are separated into the Sheep and the Goats.
Finally, the Kingdom of this world becomes the Kingdom of our Lord and his Messiah.
There are no clashes, in fact this paints a glorious picture that only God could have conceived.
It paints a picture with signs that could not be missed or mistaken for something else.
While the seventh seal and the seventh trumpet appear to be simultaneous events associated with the second coming of Christ, we cannot be so sure that the other trumpets are simultaneous with the other seals.