The puzzle can be solved with two forcing chains:
1)
r3c1=1, -> r5c1=2, ->r5c3=3
r3c1=7, ->r3c2=8, ->r1c3=2, ->r5c3=3
2)
r4c1=7, ->r4c6=9, ->r5c5=6
r4c1=9, ->r6c2=7, ->r3c2=8, ->r3c6=6, ->r6c6=7,9 that forms a bare pair in square 5, eliminating the 9 from r5c5 so that r5c5=6
The puzzle falls apart fairly easily although I think (senior moments sometimes) that there may be one or two quads that need to be recognized. Hope this helps!